Most of the pros tht shoot people, sports and events are using Canon which is what I use. The 5d is a great camera but they are coming out shortly with it's replacement upgrade. Canon's lenses are top grade for most applications and it is more the lenses than the camera body that make a great image.

If Len is renting a Rebel, going from the 5d, I would suggest he looks at the 40d instead because the control buttons are more similar and he will be able to switch cameras more easily. The Rebel is much smaller and not as easy to hold if you are used to a larger camera.

Nikon makes some great gear too. I used a Nikon before I opened my own photography studio/business