I just put in MOHH2 just to check it out after playing so much CoD:WaW.
First thing I noticed is the fluidity - the 60fps goes a long way for MOHH2. Overall, CoD:WaW has a lot more going on as far as effects are concerned. Another advantage of MOHH2 is the sound design. CoD:WaW is a bit too muted for my taste. I notice I have to turn my receiver up higher than normal to get a decent volume. Also, the sound FX for guns aren't nearly as crisp, clear, and authentic as those in MOHH2. Just squeeze of a M1 Girand in MOHH2 and do the same in CoD:WaW and you'll see exactly what I mean.
With that said, CoD:WaW >>>> MOHH2
It should be selling so much better than it is...
Hopefully it'll have legs and reach at least 500k worldwide by Xmas.