Since you're using it mainly as a travel bag I say Monty because it can be zipped close. Nothing will fall out and become lost. I do like the Tahitienne but I'd be worried about my wallet, passport, camera and stuff.
The Galliera is a great bag and holds a lot and is very comfortable to carry. And it is GORGEOUS! I would get that one if you are also going to use it as an everyday bag. But if you are going to use it specifically for travel, the Monty is good because of the zipper.