In regards to heels and faces, I'd probably say I'd prefer heels as a whole just because while both can lead to poor characters who just do the lamest most clichéd way to get the desired reaction, and do them badly, it's much more painful watching someone kiss the crowd's ass than someone who's just throwing out generic insults at them.
But I never like looking at this from a on whole perspective because there's been ton of crappy and awesome heels and same goes with faces. It definitely should be looked at as a wrestler by wrestler basis. For example, I actually prefer recent face Orton to the heel, legacy era Randy Orton we had a few years ago because Orton slowed his offense down way to much for me to enjoy his in-ring work. Whereas the face him doesn't really do the whole methodical wrestling anymore, definitely not to the extent he did back then at the very least.
That said, I voted for Tweener Bitch! and only partially because I like saying bitch for emphasis. I think back to my favorite heel turn, CM Punk's in the summer of 09 because it wasn't instantaneous and took months to actually happen. During that time of masterful character development, Punk played the role of Tweener and that's the main reason I voted for it. Just the fact that tweeners are giving more character development, at least that also seems to be the case in WWE since I've started watching, definitely gives them the edge over heels & faces.