Kokushibo is a powerful swordsman with a lot of eyes so it can be hard to get anything past him. Aizen is a master of manipulation though so that’s a challenge he would certainly welcome. While breathing arts may possibly help to reduce the strength of an illusion, Aizen can always just fall back on his brute strength. When he is fighting all out in his hybrid form Kokushibo will be unable to keep up with this guy. Aizen’s got too many tricks up his sleeve. Aizen wins.