Rillaboom can gmax, and has priority with glide. Rillaboom is also good offensive with life orb, a bit weaker but flying move is acrobatics, a bulky version with AV, and fake out support. Bulu has the ability to underspeed all the tapus, therefore getting it'sterrain up, while rillaboom has to normally run no speed evs and possibly something like 30 ivs in speed (assuming most finis have 31 speed ivs) Tapu Bulu does not have access to good stab though unfortunately, and while it has better attack and more defense and sp def, I think rillaboom is better overall. Main reasons are priority, fake out, okay bulk, and the ability to gmax.