Ehh...Tyranitar can't Baton Pass, ya' know, and what's an Unbreon?
Anyway, it's true what they say: Jolteon rocks as a Baton Passer. (I've played it as a lead on NB and it did a wonderful job. ^^) You can also outfit it with Wish to provide healing support for your team, although Vaporeon and Umbreon are better suited for that. Personally, I've never been that much into using Celebi, but I've seen the passing that thing can do, and the Natural Cure trait is a nice little bonus that keeps paralysis and other nasty little crippling moves away.
Hypello, Mullet has you beat in this argument, I'm afraid. It's a little something called team synergy: Ninjask or Jolteon start out by giving an initial speed bost, then Umbreon is passed in, preventing hazing and phazing with Taunt and trapping the opponent with Mean Look before passing it on to Smeargle who puts the opponent to sleep and Ingrains then passes on to your average Attack/Sp.Attack boosting passer. With a team full of passers (Which you should have if you want to use Ingrain), there's no point in packing all stat boosting moves on one pokémon as you can freely pass abilities between the members. Hence, the only thing a B-Pass team really needs Smeargle for is Ingrain, everything else can be dealt with by other pokémon with better statlines and more all-around usefulness, so Smeargle is really the passer with least practical value. Can it, even after Belly Drum, actually KO something that hasn't already been relentlessly pummeled by other pokémon? Celebi can. Can Smeargle take even a halfway decent attack (Physical or special) and keep going? Celebi can. Can Smeargle get rid of status problems simply by switching out? Celebi can. Can Smeargle actually be switched in against anything capable of attacking? Celebi can. In the face of this evidence, how can you claim that Smeargle is better?
