Looks like the one you want, rx-v450, is the newest receiver and incorporates the newest features as well as having the best internals from what I can tell. If you want something that will be a little more future friendly, then I'd say go with the rx-v450. It's 6.1 where as the others are 5.1, has component video switching, and appears to be a higher end model compared to the others. That was my impressions looking at those models very quickly (I'm at work, so can't look too long). Since I haven't owned or used any of those models, I am only going by the specs on the Yamaha website.
Hope that helped.