While I haven't made a decision yet, the 2 GB of RAM might be a BIG DEAL. On my original EVO with it's (i think) 512 meg of RAM I have been out of space for about a year. Don't do most app updates -- no room. Everything that can be moved to the SD card IS moved (got an app for that).
So I honestly don't know if the 1 GB on the new EVO will solve that problem permanently or just temporarily. Maybe 2 GB on the S3 is that important.
No question that has been the biggest problem I've faced on my original EVO
ram isnt the same thing as rom, ram is temporary space for running apps and rom is internal storage for apps. But anyway both phones should have plenty of available space for apps for a while, you shouldnt have to worry about it