I'm extremely happy with the MSI twin frozr, even when its overclocked the temps are still very low, idle at around 34c and doesnt go above 70 in games. Its a good size and is silent, my 120mm cpu fan makes more noise!
I would think the asus would cool alot better than the msi because of the sheer size of the cooling setup on it, but it does take up 3 slots on your motherboard, so if you've got the room the asus would probably be a good choice.
You cant lose either way to be fair!