At the risk of "beating a dead horse", regarding the full frame vs. crop camera debate; I'd like to provide my feelings on this matter "one last time". IMO, if you are shooting a 1.6x camera with top-line glass and you are getting very good to excellent results; you may improve those results by using a full frame camera.
However, if you are not getting very-good to excellent results with a crop camera and top-line lens, then IMO, you will probably not experience a photographic epiphany by switching to full frame because it is probably the Indian not the arrow that is at fault.
Expressing it in another way without the allegory, if a photographer cannot get consistently very-good to excellent results using a 60D with 17-55mm f/2.8 IS and 70-200mm f/4L IS lenses either that specific copy of the 60D has problems and/or the photographer's technique is at fault. A photographer SHOULD be able to get extremely good results with that combination of camera and those two excellent lenses. very likely sharpening might be the problem. I learned a bit about sharpening from Colin and my images are better for that.