5D is full frame so you get more bang for your buck when it comes to lenses. A inexpensive 17-40 is really a 27-64 on the 7D so for your landscapes to get 17 youd have to by a very expensive 10mm.
For portraits the full frame is much nicer. The only thing better is 120 or 4x5.
For sports the focus issues with the 7D would not make it a choice until they get them all fixed.
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