Dudley’s choice of Ultra in certain matchups is quite an interesting one, it really does differ from player-to-player.
Personally, against Ryu, Akuma and Chun, I use Rolling Thunder. It’s true that smarter players will refrain from throwing as many fireballs against you when you have this Ultra, but that is exactly the reason why I choose it. Dudley deals ridiculous stun and damage anyway, Corkscrew Cross damage is just the gravy on top of the meat. If choosing RT severely hampers one of Ryu / Akuma’s best controlling tools, I’m all over it!
Chun players won’t use Kikoken as much as Shotos use fireballs, but they will still use it from time-to-time. Usually they’ll throw out a slow one and then follow up afterwards and mixup with her buff pokes / throw / flip kick. Dudley doesn’t really have that much he can do in response to this, so this is exactly why I use RT. After experience of the matchup, you can get a feel for when Chun is going to throw the Kikoken. Just buffer up the RT and if you see her start the animation, just press 3K and bam, stop that sh*t dead. Again his removes a good tool of hers, and I’ll take that trade over a few extra points of damage.
So overall I use RT against:
Ryu
Akuma
Sagat
Guile
Dee Jay
M. Bison (Dictator)
Chun
Juri
Honda