They are quite different. Trying to edit some basic CSS or HTML code in XenForo can be a pain in the back, however you can customise quite a lot of things. However, when it comes to permissions...idk, it feels like it needs more types of moderation.
IPB on the other hand, it's easier to modify, u don't have to go through 100 files to modify something basic as the footer. This is why i prefer IPB