vBulletin VS Invasion Power Boards

Hi,
I'm making a forum and want to know which one you suggest. I have used SMF and vB in the past but IPB looks really good. Which one do you like? (and reasoning is helpful too)

Thanks!

P.S. If anyone has integrated a forum with amember before I would like to ask you a few questions if you have time. If your willing to answer them just let me know and I'll PM you.