Everything said is true, but that doesn’t mean there aren’t compelling reasons to play XIII. If you can play it on your PC, the graphics are far better. The netcode for the Steam version, while not a rollback code like GGPO, is still usable. XIII is “THE” KOF at the moment, meaning, it’s being played at tournaments, including EVO, so that’s something to consider. My local community is all about XIII, even though many of them have been serious about KOF since 98 or even 95.
Also, there are a lot people in GGPO, but they are mostly scattered across the western hemisphere. GGPO works well, so that’s not a deal breaker, but that’s just something to note. And you most of the chat is in Spanish, which sucks if you don’t speak it.
There are other difference, like drive cancels and HD combos in XIII that some people like and some people hate. and XIII has trial mode, which is cool, and custom colors for your characters.
KOF2002UM is rumored to be coming to Steam, and I believe it will have online play. If that’s the case, then 2002 on GGPO would be a good way to prepare for that.
Also, XIII was 50% off on Steam yesterday, so you missed that.