I have both bikes, but much prefer the P8. I'm a big guy too and the ride is a lot more comfortable. Both have been great bikes though.

If you get a Delta universal rack for the P8, for $20 you'll have a lighter (and higher for panniers) rack than the one that comes with the D7.

The only thing I don't like about my P8 is the color. Ultra-ultra bright red is a taste I am still trying to acquire!