They're all going to be very similar (Touchwiz based), because there aren't any AOSP roms out yet other than for the International version. Once CM supports our device, I'm sure there will be tons of roms (AOSP, AOKP,MIUI, etc.)
If you're a flash addict, like I used to be when I owned an Evo 4G, I'd just try them all lol - http://forum.xda-developers.com/forumdisplay.php?f=1881