I never really tried IPB, so I can't give an honest, balanced opinion in this message. I've been using XenForo, and no big problems so far. Each time the company releases an update, the add ons become incompatible, and it's costly to upgrade them!
I am not a forum owner, but as a forum poster I have used XenForo as well as IPB. Based on my experience, I can say both are good. But I would like to know do you have to use add ons to have a forum currency or forum points, or it is inbuilt feature?
When I first saw this topic, I was confused as to what the title meant. Till I looked properly and saw that it was for forum owners.
I think I've seen @Alexander mention the latter on another thread and I must say if that's what's in use here, it's really great.