The most important thing to remember is that a Travel Backpack is touch by baggage handlers. The abuse will be doled out by the planes, trains, buses, and by the taxi drivers, even when your arrive at the hotel someone wants to touch your bag, nobody will leave that bag alone, everyone will get their chance to break that travel backpack.
A trekking bag is not touched, it is babied around, nobody gets to touch it, only the owner who cares about the bag and does not want to break the bag. Maybe a tree or bush will touch it, but the human animal, the most dangerous on the planet does not.
Would you tie a tent on the bottom of bag that is being checked at the airport? Yes, you can do it, and if you are lucky it will make it to the destination, but let us be real, inside the bag is better.
A Travel Bag is meant to keep people out, the mountain bag is meant to allow the person into the bag quickly.
The Travel Bag should have the pockets on the inside of the bag, and the mountain bag has the pockets on the outside.
A travel bag will make a way for you to lock the bag, a mountain does not, because there are too many pockets on the outside.
A travel bag should be smooth, there should be nothing lose to catch on the bus door, to get trapped in the baggage carousal at the airport, anything lose will be broken, I 100 percent guarantee it.
A baggage handler will grab anything he or she can reach quick and fast, and pick up that bag, those clips just were not meant for this abuse.
Hehehe, you do not buy things up on the mountain, you do not come home with more then when you left, and a travel bag needs to expand so it can hold all those souvenirs.
The length of time on the mountain or out will decide how much weight you need to carry. A person climbs the mountain or goes to the jungle for less than one month, a Backpacker or Travel goes for normally 3-6 months. Climbing or Hiking is something your do for a vacation or enjoyment, while travelers live with their bag, it is their home, it is a lifestyle, not a vacation.
I tend to laugh at the Traveler walking around on Khao San Road with mountain climbing gear and think, too stupid for word, they went to a gear shop and the salesperson sold them 100 percent the wrong gear. The more pockets the outside, the more I know they know nothing about traveling the world.