In addition to what's already been mentioned, I want my travel bag to have security features (Pacsafe is a good example) like secured zippers, one end of strap removable to wrap around chair rungs, wire in strap to prevent slashing, wire mesh embedded in main part of bag to prevent slashing. I have one bag that can convert from cross body purse to backpack, very handy.

Good brands of travel purses include Eagle Creek, Baggallini, and Pacsafe. I tried Travelon and found the brand sorely lacking in quality.