I’m going to list all of the significant ways I can think off why Ryu is better than Ken according to the USF4 arcade changes.
Slightly more damage off of SRK FADC Ultra
EX Fireball knocks down and is faster and Normal Fireball has 1 frame less recovery and start up
More damage if you land a j.mp
Faster (but more punishable) sweep
cr.mk has 3 more active frames and 1 less recovery but is 0 on hit as opposed to +1 and -2 on block as opposed to -1 and starts up 1 frame slower.
more invincibility on ex srk
m.srk is 3 frames as opposed to 4 mediated by the fact that delayed wake up will largely eliminate 4 frame safe jumps
Standing rh anti air, standing fierce comes out faster (better anti airs)
Better super
cr.mp combos into sweep
tatsu knocks down, is safe if blocked standing, and is better for better getting over fireballs
double hitting moves to break focus
The bolded points are the ones where Ryu is strictly better than Ken. So now you have to ask yourself why you should stick with Ryu. Your Ultras do about the same damage now (with animation Ken’s does more), your fireballs do the same damage. You barely ever land a j.mp in the first place, I guess you are supposed to fish for it now. You super is better, if you ever get it and didn’t use your meter for j.mp xx ex tatsu instead (lol). Really, the only practical advantages you will see in every match are: better anti airs, slightly safer fireballs and a better tatsu, all of these advantages already exist in AE 2012.
In exchange Ken gets an amazing kara throw, leading to great frame trap/throw mix ups and now he can stutter his jabs and combo into sweep. He gets a long range normal (step kick), and a long range overhead that is safe on block. Ken’s ambiguous ex air tatsu is still there, I believe all they removed was his escape tatsu. Ken is still weak to focus attacks from outside kara grab range though.
I don’t know, I’ll still stick with Ryu at the start but I’ll try out Ken and make the switch if I’m just getting better mileage from his long range pokes, kara throws and air ex tatsu