Smogon for me, the tiers make the game a lot more interesting and balanced.
Many of smogon's clauses were introduced by GF them self. Banning Soul-dew, species clause, banning base 670 legendaries, sleep clause, etc. were all introduced in PBR/battle facilities ingame.
And thank god for Smogon. I hated smogon initially but my early random-battles in gen 5 taught me how terrible a metagame without bans and tiers is. Imo, stepping into battling properly made me appreciate the job smogon is doing.