Even through PhpBB its easier to customize and administrate, IPB comes with a lot of mods that you´ll have to install by yourself in PhpBB...althrough PhpBB gives out much more errors than IPB and IPB offers more opcións than the other...the reason (I think) for PhpBB to have more developers is that it comes with just a few things and they can do all the other options ofrom the others forums like and add-on to PhpBB.