If you're fighting fire based creatures, the ogre lord.
If you're fighting anything that poisons (including mages), the arctic ogre lord
If you want a fun friend that will kill itself, the Meer Eternal (really, they do! If they don't kill you first)
Orc Brutes aren't that bad either (but don't hold up to the ogre lord test)
If you have a different tank, you could do a lot worse than titans.
But just to be safe, go with the frosty ogre lord every time.