OK - here's my two cents for what it's worth. Theoretically, if I had to choose between a good play caller/bad game manager and a bad play caller/good game manager (although I can't imagine things being that cut and dried), I would choose the good play caller every time.
Why? Because it would be much harder for me to compensate for a bad play caller (this would involve doing things I preach against such as make-up calls, figuring out a way to overrule a partner, deflecting crap from the howler monkeys toward him, etc.) than it would be to compensate for a bad game manager. I think its because I have enough self-confidence (some would say
ego - OK, most would) in my own fantastic game management skills that I could easily overcome any problems a partner might cause.
Of course, that doesn't include standing between a partner and Bobby Knight, for example.