I have both cameras and they eventually perform similarly.
I think the handling of the 620 is superior, the viewfinder is better, the autofocus is better... and Canon glass is excellent.
No intention to start a Canon-Nikon war!
However if you use the camera in P or in shutter-priority, there is almost no difference in usage, in Aperture-priorityon the canon you use your dial, on the nikon the aperture ring.
What makes the difference? The glass you have! Now I have more Nikon glass and it is cheaper to find apparently, so I use the F90 more, but when I my Canon glass sufficies, I use it!
The F90 is much heavier... but takes Alkaline batteries, which last less and weigh more, but are readily available. So... it is up and down.
If you leave your Canon "on" it will eat your batteries in a couple of days, at least, mine does.
