DC to arcade similarities - Arcade feels slower if you’re playing DC on a not so big screen. Big screens feel slower IMO. I play on a 34 inch screen for both and they seem the same. Every single combo and play is possible on both, so they probably have the same exact 60 fps, and 1 frame moves on DC are still one frame moves on arcade. I’m sure Magnetro knows more about it. Anakaris + Cyclops inf also works and it is actually very easy. I don’t know why that urban legend got so popular.
Differences - The order of the charaters on the select screen is different. There are a couple very specific gltches that are different from japanese arcade to US arcade, from japanese DC to US DC, and from arcade do DC in general. I’m not sure which works on what though.
XBox - You can kill the character that is getting out on a VC.
PS2 - Same as Xbox. Some hitboxes are slightly different, although it is very hard to notice (I think Wong noticed that first). Sound is awful. Any time you get a lot of stuff going on the game will have slowdown. Game seems uglier to me.
One thing I would like to see is the PS2 version running on a PS3, if possible. Maybe the hardware can get rid of all the slowdown problems?