A factor being largely overlooked because the PS3 advocates THINK they know the answer is what sort of controls will be used. Motion control is not going away so this is only a non-issue if the PS3 has completely transitioned to effective motion control itself. I somehow suspect the core supporters will never allow this.
In which case the choice will be very important. I'm pretty certain I know how this will go but lets look at it this way. It seems to be a consensus that most growth, non-traditional, female, young children are being recruited by the Wii. Can this group be persuaded to give up the simpler intuitive controls even for the "perceived" benefits of the traitional.
Historically there is very little evidence that people move in that way. It was relativly easy to lure people away from the typewriter to the more autoated word processor, few ever returned. Driving enthusiasts prefer manual transmissions but by percentage, they are a small niche.
Good luck on getting to switch control systems.