The larger pixels of the 5DII mean you can stop down further before diffraction begins costing you sharpness in your landscape shots.
If you consider equivalence, you'd need to stop down the 5D2 shots more than on the 7D to get the same depth of field, assuming you have already use the correct focal lengths for the same field of view. So there is no benefit to the 5D2 there. If anything, if you're going pixel peeping, the 5D2 would then be worse for diffraction since it has more of them.
Even for noise, still considering strict equivalence, the 7D is generally superior to me since when you go fishing in the shadows it is less prone to show banding. The only benefit I see for picking a 5D2 over a 7D is if you need the shallower depth of field that can be attained with lenses that exist.
The other apparent advantages of a bigger sensor only come into play if you don't need or care about strict equivalence.
Why would one shoot strictly for equivalence? FF gives you the option for shallow DOF and faster shutter speed. Given a trade between faster shutter speed and shallower DOF versus not getting the shot due to blur, I'd choose faster shutter speed and shallower DOF. I'd rather shoot a 5DII at ISO 3200 in a dark auditorium rather than a 7D at ISO 3200. The same lenses will also result in higher resolution (lp per image height) on a larger sensor.