Consider some of the following thoughts as you make up your mind: the type of combat you want to be involved in your role in said combat your chances of survival the amount/type of loot you might get or even why you wouldn't want to follow a certain boss Share your ideas!
Why is there no option for The Beast? That Boss stomped half of the Imperium and crippled the SM, even if he's mentioned in little more than a sidenote.
Ah, I only considered 'active' orks. I imagine it would be hard for you to go into detail as to why you'd follow him specifically, other than that he was successful.
WTF?! WHERE IS WARBOSS GORGUTZ Ead'UNTER! you git... http://warhammer40k.wikia.com/wiki/Gorgutz_'Ead_'Unter
I'd pick Dok Grotsnik. He is crazy enough to have us charge at everything in a straight line, and some of us might even survive, since he'd make us cyb-orks... and it's never bad to have a Dok around when you can't stop da chop...