"If I were to shell out $$ for another pack, I would want something I could use for hikes and backpacking, so I would be wary to get the Porter. "
I totally agree — except the holy grail — the "do it all and do it the best" backpack is oh-so-elusive!! It's why so many of us have multiple packs!
Travel Pack — A travel pack — esp. one that may be checked in from time to time — needs to be built tough. Ideally, it also needs to afford protection for its straps and belt. And because few of us need to completely pack and unpack every time while on the road — it should be designed with easy opening and well thought out compartments for organization. Most travelers "hike" relatively short distances (e.g. train station to hostel) — so a beefier pack with different compartments (preferably lockable) and other features at a cost of an extra pound or two in weight is a sensible compromise.
Hiking Pack — When hoofing it for hours on end day after day — I care much more about comfort and light weight — and much less about "travel friendly" features!! When hiking, I bring only the essentials, and I don't add "souvenirs" along the way. And thus, I tend to unpack everything each night anyway — so a "one big hole" design is just fine — I really don't need a myriad of different zippable/lockable compartments! I also don't need beefy protection for straps and belt against airport conveyor belts.
As you can see, the needs for these two types of travels are very different — and some almost contradictory. But what if I plan to hike as part of my travel??
(1) If hiking is the greater part of the journey, then I'll bring my hiking pack. Comfort trumps convenience. I'll have to be very careful about protecting my hiking pack though.
(2) If just a day hike here or there — then I'd use my travel pack. I can always lighten the load by leaving unnecessary stuff in the hotel. Or I may bring along a supplementary UL backpack or day pack.