So I've played Tatsunoko VS Capcom FINALLY and...

SF2 to CE was minor, as was CE to HF. HF to SSF2 was huge, SSF2 to ST was huge too.

but it was just an analogy, the localized version is updated basically. It was awkward to play the arcade version a few weeks back after playing the US version.

 

I suppose it depends on what tier level your skill is at. Higher grades will yield more differences in game play, while the average Joe might not notice anything.

 

The biggest change for me between the US and Japanese was the music. The Japanese version had the best music in a capcom fighter, where each time you tagged out the fighters theme would pop up. Going from the Gatchaman theme to Street Fighter Ryu's theme was awesome.

This is gone in the US version.