Frankly, the HMG Porter in all 150D hybrid-cuben would meet your needs better than all Dyneema X. The regular 50D is bomber stuff, and unless you're doing serious canyoneering, all 150D would more than meet your needs. I can't see an advantage to all Dyneema X on any front. I'd get the 3400 Porter because the extra 15 or so liters comes from the extension collar, which adds negligible weight to the total pack. I rarely carry more than 40 or so liters in mine, but it's nice to have the option to add more when necessary.
Plus, I have to say that I have worked with a lot of cottage companies--nearly all excellent-- and several major retailers, but HMG's customer service is the best experience I've had yet.
If you want side pockets, Zimmerbuilt's options are great.