My two cents....
Barbarian
+Barbarian Spiritist Hammer twink weapon
+JBB
+Most think they look better. Hot females
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+Medium sized
Ogre
+Great overall stats
+Frontal stun immune (though spells still get interrupted)
+JBB
-Fatty
Troll
+Snare Clicky. Situational, but only shaman with snare ability.
+Regeneration
+JBB
-Fire resist penalty (minor, but there)
-Fatty
Iksar
+Medium sized
+Good Wis
+Regeneration
+Stone of Morid for fire/cold resist
+AC Bonus? Unsure how much this helps though.
-No Jbb
In the end, geared and fully spelled, race isn't a big deal.
Regen doesn't matter much with topor ticking away at 300 a tic, but still always helps to some extent. Very nice if not twinked with a fungi and/or not a 60 torpor shaman yet.
JBB's usefulness fades away after lower 50's, but is still a very nice item.
Front stun immunity is great, but not as big a deal as some make it out to be. Stuns still interrupt your spells, they just don't lock you for two seconds.
Troll snare clicky gives you the option to snare. It's usually not practical given it's long cast time and weak snare, but if you
must to prevent something from running, it's there.