what's the best forum software?

so far i really like and think Xenforo is one of the best software that doesn't feel like it's still in the old age unlike vbulletin.
what i wanna know is what's better mybb/xenforo/vbulletin/invision power board?

Please note. if you're going to post make sure it's a useful comment with proof that backs up ur claims on whats the best forum software.