My Shaman is a troll, I've enjoyed playing him, but were I to do it over again, I'm not sure I'd be the same race.
The special regen is shared with Iksar, Ogre stun immunity was still broken lat I heard (could be fixed, I dunno) and Barbarian is maybe the easiest to lvl, with fewer faction problems and less exp penalty.
In the end, I don't think there's a clear winner, play what waves your flag.
As a Troll/Ogre/Iksar you can kill Bards, Millers, Dwarves, and pretty much every races' guards with wild abandon, cause your faction is already FUBAR. As a Troll, I've trashed Gnome, Dwarf, Halfling, FP, Qeynos, Paineel and Barbarian faction killing their guards and NPC's.
As a Barb you can kill Neriak Guards, Grobb guards, and Oggok guards with that same wonton glee. I suppose you can kill Dwarves, but....
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again, I don't think there's a clear winner, play what waves your flag.