How much weight are you carrying in your pack? I'll switch between a pack and pans depending on my ride, but if I know I'll be carrying a heavier load, I'll usually opt for pans because:

It's easier on my back
The center of gravity is lower
I feel less restrained

If you're carrying enough weight where using a waist strap would seem like a good idea to keep the pack from shifting around on you in transit, maybe considder pans?

The Northface pack looks like a good little pack, there are some other good packs put out by Ortleib too.