Nikon D40 or Canon 450D? Which one's the better deal?

It doesn't make much sense to compare these two cameras.

Better pairings would be:
Nikon D40 and Canon EOS 350D
Nikon D40X _OR_ D60 and Canon EOS 400D
Nikon D80 and Canon 450D

The D40 is a lot cheaper because it has fewer functions, lower pixel count, blah, blah, blah.

At the moment, the 450D might beat out the D80, but Nikon is due for a new issue that you could really compare to the 450D. If you want the latest and greatest, hold off a few weeks and see what Nikon brings to the table.

But to strictly answer your question...

The D40 is the better deal, if you are considering bang for the buck. The 450D is the better deal if you are looking fomr the newest camera simply loaded with features. It's your money, so it's your choice. They are not really in the same ballpark, though.

i think the D40 doesn't have autofocuse motor

The difference between the two cameras has more to do with subtleties that only an experienced photographer would care about.

The picture quality, etc. is the same.

Get whichever one you like. Don't drive yourself nuts trying to compare.

I have used both Nikon and Canon DSLR cameras and speak from experience.

I am working professional photographer and in my business I have chosen to use the Nikon system cameras, not because they take better pictures (I consider the Nikon and Canon systems to be of equal quality), but because under the less than camera friendly conditions I encounter taking most of my pictures, the Nikon system seems to last longer, be more durable and rugged, and require less maintenance than the Canon system cameras.