I like the sound of the Yamaha better, using Infinity Alpha series speakers.
Just a couple questions to ask yourself:
Do both models have all the audio and video hook-ups that you need (possibly including the dreaded x-box and computer) ? Do both have any second room capabilities you might want ?
Also worth considering, can you make do with a five or six channel unit from last year that might have a little bit better overall sound quality at the same price ?