Well lets see, Bibarel has Simple which doubles stat boosts and reductions+ he gets Curse in Platinum..... Now if that isn't enough for BL then listen to this. If Bibarel gets these EVs 216HP/40Atk/252Sp.def and Sassy Nature.... and pulls off a Curse then its pretty damn strong..... with this and the fact that he gets STAB Quick Attack. If you truly love Bibarel you can move him to BL or keep him UU if you still think he needs more power.

Compared with other BL pokemon such as Ursaring or Flygon, Bibarel seems a little weaker. However, with the Curse move up its sleeve, it bypasses most UU pokemon.

I voted BL.