ATA

ATA is short for Attack Accuracy. It's what governs your ability to hit enemies, and also governs what guns you can and cannot use.

ATA vs ATP?

ATA is often lowered on weapons with high ATP, as to balance things out. However, this often changes what weapon choice people use; some people, for example, may go Wild for ATA (for example, they are a low accuracy race such as beast), while others choose power. The argument has been going on since the game's prequel, Phantasy star online; Normally, people choose ATA over ATP