Hugely disagree, I think it's the other way around. IPB (especially the new IPB 4, MLP Forums runs on IPB 3) is incredibly functional and looks amazing. xF is new, yes, but last I checked, it's caught up in a lawsuit, which prevents it from any major updates, leaving it in design purgatory indefinitely (if this has changed, apologies).
I think xF is a fun idea in theory, but in terms of actually working, it will prove incredibly inconsistent in terms of continuing the aesthetic across Poniverse. Just meh opinion tho