Hi Steve
I personally had the chance of a 1D Mk II just before Xmas and the deciders for me not to buy was the Weight, screen & sensor size, and also it has no live view.
I have a 7D so the main advantage to me over the 7D is the f/5.6 AF restrictions on a none Pro body.
So I personally would go for the 5d MkII for those reasons.
Whatever you chose to do If you buy at the right price and feel its the wrong decision you should be able to recoup most all of your cost if you sell it on quickly.
Regards Ian
.