Jeff, I've had both the 2.5-8x36 and 3.5-10x40... they're both excellent scopes. Really, I think two of the very best all-around scopes Leupold makes.
The 3.5-10x40 is probably my favorite Leupold scope, but I tend to pick scopes based on how they balance on a rifle, both size-wise, and weight-wise. I'd go 3.5-10x40 on the 8400 WSM and 2.5-8x36 on the 700 7-08, but there's no "right" answer... BTW, the 3.5-10x40 is 2oz's heavier than the 2.5-8x36.
