Are you say ef is not a sound decision? EF lens on a crop are very good - better than on a ff in most cases
I didn't put this as precise as I should - I was talking of the whole eos system with the ef mount (bodies, lenses, flashes etc etc and 3rd party equipment that only works along with this system). Basically the reason why there only is limited competition between manufacturers, unlike say the pc where you can plug in any gfx card you want.
And being a "system", I think is important to provide every customer in every stage of photographic experience with a longer-term, somewhat competitive, adequate "off the shelf" offer w/o forcing him/her to sell equipment (ef-s anyone?). And this is where Canon is temporarily lacking, it's not just Nikon trolls, but there is/will be a gap between consumer aps-c and 5d3+24-70ii that is too wide for some. The fact that many ef lenses shine on aps-c doesn't fix that.