Mobile access and posting pix from mobile devices is important for my forum. In comparing IPBoard and XenForo. TapaTalk for XenForo allows users to take and post pics via their iPad. IPBoards which has it's own iPad app does not have that feature. It does look like I an IPBoard owner can add Tapatalk hook.
IPBoard has good mobile theme support. XenForo is still lacking a native mobile theme in the current version (although at least one add-on exists to add one). Regarding TapaTalk, both Xenforo and IPBoard support Tapatalk. As a user of multiple forums, I find TapaTalk the best way to post from my phone. I rarely use the mobile site on a forum.
XenForo has a more modern look and feel compared to IPB, if that helps your decision-making.
More making a statement. The IPBoards iPhone/iPad app is less adept than Tapatalk, the Xenforo option, as Tapatalk allow uploading of pix from the iPhone while IBoards app does not. Though IPBoards said they are working to fix that in next version.
Because IPB wants users to purchase their app and it competes with TapaTalk. Reasonable to expect IPB to push it's app to IPB forum members who would then have a less capable mobile access. Telling them they need to get another program might put them off the forum.
Maybe true, but if Tapatalk is doing it better, I'd be inclined to use their product instead. It's great to have options and an app like this doesn't need to be considered a core feature of the forum software, in other words I wouldn't make a buying decision based on a factor like this. On the other hand, if they were to make it a core feature, to the exclusion of other options like Tapatalk, then that could very well be a good reason to avoid their products altogether (not saying they'd be foolish enough to do that).
Now if you could only fix it for Android and Windows. Even on smartphone with Apple at 20%, Apple is the "decider" as it all has to work on iPhone and Android and Windows will follow. iPhone is concentrated while Android is all over the map with high end and low ends with Apple all high end.
For forum software, if it has a good iPad and iPhone interface to users, it will work for the rest.