You are on the right path of comparing IQ as the most important factor in choosing a camera. "Feel" is the worse criteria to use in choosing a camera. The moment the viewfinder reaches your eye the only feel you have is in the shutter release finger and eye.
Remember when you purchase a dSLR that you are getting a camera system. Both Canon and Nikon have more than sufficient lenses and accessories to satisfy most photographers. If you are into something extraordinary ... say astro or macro ... make sure the camera system you choose supports that specialty with hardware and software.
Canon hardware seems to be a tad cheaper than Nikon for equal/similar equipment. One of the prime keys to low-noise at elevated-ISOs is a CMOS sensor. All Canon dSLR cameras utilize CMOS sensors ... only the most expensive Nikons use CMOS. So if you ever need/desire a second body you will have more choices and less expensive choices with Canon than Nikon (using low-noise at high-ISO as a prime consideration). The 5D has held the title of low-noise at higher ISO for quite a few years, the latest high-end cameras from Canon and Nikon has stripped the 5D of that title ... but the difference is not visibily significant.
You won't see a significant difference in IQ between the 40D, D90, 50D and/or a 5D up to an 8x10. It takes 50% more MPs to make a visible difference in IQ. The MP difference between all the above cameras is insignificant.
Nikons are far more sexy looking than the chubby Canons (this is important in my book.)
Personally, I feel that with the D90 or the 40D/50D you will be completely happy. Both camera lines are designed for the human hand and one will easily adapt to either manufactors design. I would probably go with Canon because of equal but less expensive lenses and due to the greater and less expensive choices of low-noise, high ISO cameras.
A few photogs that I respect have recently purchased the 50D. Initially they were really disappointed with the performance ... but they learned that had to turn-off all the in-camera noise reduction handlers and viola! They feel the resolution is superior to the 40D.
Gary
PS- It is hard to qualify opinions on the internet ... should you choose/consider a person's opinion as a deciding factor make sure you visit his/her photo site to help you qualify their experience and skill level.
G
PPS- Direct comparisons between Nikon and Canon are not easy because they tend to stagger their cameras features and prices. If you had a stair with the lowest step being the cheapest camera with the least features and the top step being the most expensive camera w/ most features.
The steps will alternate between Nikon and Canon with no steps having both a Canon and a Nikon.
G
PPPS- All things being equal ... then go for "feel" as the last and least important qualifier for a camera purchase.
G