Cats can also handle a harness and a leash a lot better than you think, especially the friendly, outgoing cats. Just don't expect them to be able to keep up with you like a dog. Cats move at their own pace and will protest if you try to force them to go with you. Let them lead the way, and expect to spend a lot of time standing around in one spot.

Basically what I'm saying is that leashes work best if you're not in a hurry to go anywhere in particular. Backpack if you are.