B-line,
It was a couple of reasons:
The 5D has 3FPS, while the 40D has 6.5, I shoot more action stuff than landscapes/portrait.
Cost was a factor too, I'm just a hobbyist and didn't see the need for a $2800 body
I used the extra money on more L lenses lol (100-400L is next).
Re: flash, the onboard flash wasn't really a decision point either as I have a 550ex and 580ex, and a couple of slaves that I could have used with a 5D. It is handy to have an onboard though for fill flash. (Having to carry around an add-on flash and keep the batteries/battery pack charged is a hassle sometiems too)
Nice shots btw-