My build allows either of these(nearly no use for spirit, no way to spend how much either give), and I'm farming a1/a2 with ~50k dps. I'm unsure which to use though; and more importantly which runes to test against eachother.
I don't really like way of a hundred fists: I find you're standing still far too long. Fists of Thunder though is very quick and has the knockback at the end, which helps a lot with reducing damage taken.
Thunderclap does better single-target damage, procs more life on hit, and builds spirit faster. The only advantage of hundred fists is the tiny AoE is full damage, plus whatever rune effects.
My build allows either of these(nearly no use for spirit, no way to spend how much either give), and I'm farming a1/a2 with ~50k dps. I'm unsure which to use though; and more importantly which runes to test against eachother.
So yeah: I'd go for fists of thunder personally.