If your main concerned is relatively normal size poster prints, the theory and stuff is great, but I bet you're going to MOSTLY care about this answer right here:
Mpix.com - Help
It's interesting to note that those are OPTIMAL results, and more or less correspond to 300dpi. However, from normal viewing distances, you'll find that 300dpi isn't necessary. They even point out on another of their pages that 6mp images tend to do just fine for their big ol' wall clings:
Mpix.com - Wall Clings
I know, for me personally, my camera may not actually out resolve all of my lenses, but it certainly out resolves my skill level. My hunch is that either of the full frame sensors is going to out resolve all but the most extreme uses as well.