I wrote this hella long ago - like over 4 years I think. It’s not 100% accurate but its pretty damn close.
Super Street Fighter 2 Turbo (ST)
An In-Depth Look at Old Characters
Derek Daniels
With the advent of ST being released on Dreamcast, there seems to be a resurgence in questions pertaining to old characters. Everyone is wanting to know how to pick them, what makes Old Sagat so much better than New, is there even a reason to pick Old Blanka, etc. With that in mind, I will attempt to list as many differences as possible that I know of, and hope that some of you guys can fill in some of the blanks that I am missing in an attempt to make this as accurate as possible.
Lets first discuss what Old characters universally do and don?t have. The biggest difference is that they automatically lose the ability to perform a super move and the ability to tech throws (no one can tech holds in this game). Since overheads and juggles are all new to the Street Fighter engine, they can?t perform these either, although they can be juggled, etc. They also gain all the good colors 
One of the biggest misconceptions that people have about the old characters is that they are exact replicas of their SSF2 counterparts ? which isn?t true either. In most cases, they are completely unique from how they are in SSF2 and ST. Keep reading and you will see what I mean.
I will also include the exact command for all old characters. So something listed like, Zangief ? RLLL means to pick Old Zangief, the controller motion is press any button to select the character (except start and hold button?) then move joystick Right, Left, Left, Left and hit Jab for 1st player color or hit Jab+Short for 2nd player color. Also if at any time I simply type a name, like Vega and I don?t prefix it with O.Vega for Old or N.Vega for new, just assume I?m defaulting to New.
O.Ryu ? RRRL
While O.Ryu does lose the jumping Strong juggle, the Toward+Strong overhead, the Toward+Fierce rushing punch ? he gains a much faster fireball and recovery on his fireball. You can almost play him like Ryu in A2 ? trying to Fierce Red Fireball everything in your path. This alone arguably makes him better than N.Ryu in some people?s minds. His Roundhouse Hurricane kick also spins one less revolution than New ? which comes in handy now and then, especially when going over sonic booms, low tigers, etc. His Dragon Punch returns back to being completely invincible, which in all honestly doesn?t make that much of a difference. Last but not least, he retains a few combos that his New counterpart doesn?t possess due to Far Standing Roundhouse buffers. You can do Crossup Roundhouse, Low Strong, Standing Roundhouse into Fireball versus Zangief ? N.Ryu can?t.
O.Ken ? LLLR
The differences between N.Ken and O.Ken are probably the biggest between any 2 characters in the entire game. N.Ken gained all sorts of new moves that have become staples to Ken?s design in the Alpha series and beyond. The main things to take note of are that O.Ken?s Fireballs behave much differently, Jab is really slow, Fierce is really fast. His Dragon Punch is back to being invincible, which like Ryu doesn?t make that much of a difference. He can cross up with Jump Roundhouse, New can only cross up with Forward (which is a much better cross up), he loses the air throw that New has, as well as the Knee Bash that New has. Some of his normals have been changed also, like standing Roundhouse and standing Short. O.Ken is an amazingly solid fireball trap character.
O.Honda ? UUUD
While N.Honda did gain some truly frightening things, such as his Ochio and the ability to store it, O.Honda picked up a few things as well. Although he has lost the ability to charge while doing the hands, he is capable of controlling the hands, unlike New. His normals have also gone through major changes as well ? Low Fierce can now buffer which allows for some good trap patterns. Not only that but he has more knockdowns than other character. Standing Short, standing Forward, standing Roundhouse all knockdown, as well as low Roundhouse and low Fierce. He has the potential to knock you down and go for bear hug ticks nonstop. The hit box on his Low Strong seems to better than N.Honda?s as well. He unfortunately loses the cool controllable jump straight up Fierce that New gains.
O.Chun Li ? DDUU
While so far I have been able to not only make a case for playing the old counterpart but have seen really good O.Ryu/Ken/Honda?s ? I can?t find any reason to play O.Chun. There are only two differences that I can even think of. First, her flip kick ? Back or Toward plus Forward kick buffers?but it?s not like you can put it in a real combo. Her Spinning Bird Kick keeps the old motion and also hits on the way up, so she can hit crouching opponents. Still ? losing a store-able super and her new rising kick are too much for me.
O.Blanka ? LRRR
I really don?t remember what Old Blanka gains. I?m pretty sure he gained some new weird buffer, like strong or something, but I forget. However, O.Blanka isn?t half bad, although N.Blanka is still much better. The general Old Character trait of being able to walk faster helps out Blanka a lot when playing foot games against characters like Guile, DJ, etc.
O.Zangief ? RLLL
There are two main reasons why to pick O.Gief, first and foremost is losing that damn back or toward+strong/fierce hop move that New gained. I guess it has its uses, but I try to stay clear of it when I can. The second big reason is that his SPD grabs much, much faster than New. It is much harder to reverse out of SPD ticks with Old when compared to the same ticks with New. The loss of the Green Hand is usually neither here nor there versus most. He survived for years without it versus essentially the same cast of characters.
O.Guile ? UDDD
Along the same lines of how O.Ken is a very solid fireball trapping character, Old Guile is very very solid. His Back+Short returns to being a standing Short, not a hopping knee like N.Guile, which means he keep charging while poking with standing Short ? which is helpful versus Dhalsim?s limbs and when playing foot games. His backhands stays as either back or toward+Fierce, where as New is only Toward+Fierce. Same concept ? he can backhand while charging back for a sonic boom. The main thing that he loses is the cross up Short that New gained with ST. Oh well.
O.Dhalsim ? DUUU
If Ken gets the award for biggest difference between New and Old, then Dhalsim gets runner up. Old Dhalsim doesn?t have control of his limbs, which is helpful in some situations and sucks in others. The lack of limb control is almost the #1 reason why everyone plays old, but there a few other things that stick out. Some of his far limbs buffer like his marvel incarnation! Far standing Forward and far standing Strong buffer, I think those are the only ones, something else might but nothing is coming to mind. I?m pretty sure the second hit of his headbutt (up close Fierce) buffers?but I hella forget. Overall, I think N.Dhalsim is a thousand times better.
O.Thawk ? RRLL
One of my overall favorite character in ST ? I played Old Hawk for like 6 months straight one time, even playing and winning with him in one of my tournament matches at B4. The main reason why I like Old over New is the faster walking speed and the fact that I suck at doing 720 supers in ST. Old also gains a cross up that New doesn?t have ? the down+Fierce splash. New also has a cross up that Old doesn?t have, jumping Forward. I think some of his normals have more priority as well ? most notably low Forward, standing Forwad and standing Roundhouse ? but I could be on crack and be wrong, it?s just how it feels to me. The opponent is forced into block stun on far Standing Roundhouse/Strong ? new it can go over their head if they are blocking low. I also believe that his Dragon Punch is either invincible or more invincible than New?s. Plus his old colors rock 
O.Cammy ? UUDD
I know there is something different about this hooker, but I really forget. I can?t remember if she has different link combos, or a different cross up or what. I also wanna say that her spinning knuckle has more invulnerability than New. Anyone remember? Kris?
O.DJ ? DDUU
Another one of those, ?Why would you play the old incarnation? characters. The only thing I can remember being different is that Low Strong buffers. His Machine Gun Uppercut might have some invulnerability to it, maybe not.
O.Fei Long ? LLRR
The main reason why you see Old Fei Long picked is because he can buffer Rekka Ken off of every normal but Low Roundhouse. So he can poke with Low Forward and buffer that into Rekka Ken or he can do Meaty Low Fierce, Standing Strong, Far Standing Fierce into Rekka, etc. I?m not too sure if there is any difference between his flame kick though, prolly not is my guess. I think some of his normals might be different also, like standing Forward or something seems to be coming to mind, but I may be wrong. I do know that his Jumping Toward Roundhouse is different than New. I don?t think he can cross up with jumping Forward either. I?m sure JSJ can flesh this whole section out way better than I can.
O.Balrog ? RLLL
Loses one of the best supers in the game. But if you are going to play him, the only things to take note of that since he loses Low Rush, all of his punch rushes hit crouching characters. I believe the hit frames for Jab Rush is faster than Low Rush. Supposedly his standing Fierce is better also, but I have never really tested this. He also loses the cool guidable jump straight up Fierce that New gains.
O.Vega ? LRRL
Talk about a worthless old version ? is there anything good/different about him? I wanna say standing Forward buffers with him that doesn?t buffer with New ? but I forget if it?s close or far. Even if it does ? who cares? Anyone got anything with him?
O.Sagat ? UDDU
By far the best old character incarnation, he is arguably the most interesting version of Sagat ever. The main things you need to know is that the recovery his low tiger is by far much better than New. This allows him to not only fireball trap him better than ever, but he can just throw low Roundhouse tigers over and over half the time. The second thing to take note of is that he can buffer off of the first or second hit of his standing Short (standing Forward as well?) ? which means he keep opponents out with far standing Short buffered into Low Tiger. The only ?bad? I can think that he gains is a little more recovery on blocked Tiger Knee.
O.Bison ? DUUD
The only thing that comes to mind is he retains the old version of that charge down, up+punch move ? you can?t control it like you can with new. I forget if his standing Short is as good as new or not, but with the lack of Jumping Strong ? he sucks.
Thanks: The entire ST community.