Day 1 most likely, for PS3.

i think the 360 version will sell over 2 million lft.
ps3 version will sell over 3.5 million lft.
combined at least 6 million total

Day 1. Xbox 360.

I'm buying it on the X360!

Day 1 PS3 of course

If I actually have the money I'll get it on day one, for the 360 since I don't have a PS3 although I'd buy it for that if I had one.

that won't happen.  there is too big of an install base difference in NA.  Look at devil may cry 4, a former sony exclusive that sold more on the ps3 in every territory except NA.  The only multiplat games that have sold more on the ps3 in NA are very obscure niche games. 

Final Fantasy is not obscure, and with the 360 having quite a big advantage in RPG's, I don't see how the ps3 base could buy more than the 360.  I agree that worldwide it will sell more (mostly because of Japan), I just don't see it happening in NA.

I'll probably get it a week early. Even if I don't work at GameStop at the time, I'll still have friends that can help me out. ^_^

PS3.

This thread pops up every month it seems...

i think the only people that will buy ff13 for 360 is the people that dont have a ps3
but then again most 360 owners are shooter fans and love their daily dose of halo 3

sorry if i sound like a sony fanboy but its just my take on this subject