Two very different games btw.

AA is very realistic in which it takes not much hits to kill and very tactical. Its a lot harder and takes more skill. Mainly planning an attack and sending out smokes to block your enemy from seeing you and quickly taking them out.

O7 is more casual and you just go out and start shooting. There is planning but less so than AA. Its more fun IMO cause its more unexpected and usually gets more crazy. With AA there is a lot of camping so kills are slow.

O7 is faster and has more action.
AA has more realistic vibes and uses more than just quick fingers to win a match.