Full set of new lenses for my 7d

Well, size and weight for start (760 gr versus 1050 gr) and a constant f4. Secondly, on a APS-C body, the 70-200 f4 L IS is one of the two sharpest zooms available on Canon (the other being the 70-200 f2.8 L IS II). Third, if you want to get a bird or a plane, 300 mm is not enough (that is the great advantage of the EF 100-400). In my case, I have the Sigma 150-500 which is normally glued at 500 mm for those purposes.

Miguel