When we say terrible, we mean in the technical sense. As in, people will get randomly signed off of PSN during a match or a lobby (resulting in a loss of points in Ranked), truly horrendous lag against certain people that feels as if the characters are wading through a solid block of molasses to beat the crap out of each other, and twice I've had the game freeze on me during the online VS screen (the one where it shows both characters that were chosen and what ultras were picked) where I had to restart the PS3.
But since you said you barely play online then it really shouldn't matter unless you plan on competing in tournaments. In which case you'll notice that the timing for your combos might be a little bit off when trying to do it on the 360 version. Other than that, nothing I can think of.