I voted GoT because they are far more treacherous, and aren't bound by the notion of 'good' and 'evil'. They just are, and will do whatever they have to to win.
GoT all play to win, because if they don't they die.
LotR characters meander about taking the scenic route, stopping to have tea with balrogs, dance around with elves and then they finally defeat their greatest villain by throwing some jewelry into a bonfire.
I just can't see LotR out-witting, out-playing and out-lasting the GoT characters.
Although, LotR does have a lot more convenient plot twists, so it's got that going for it...
You know, just as GoT are about to win, the eagles show up and eat everybody or whatever. The end. No wait, it's LotR so now you get another three hours of endings.