The Outward Hound was the first one he got. We went throught it pretty fast. We mostly used it for snowshoeing. The plastic got weaker with the cold weather and people would try and grab the handle on top during expedition, hoping he'd lead through the rough patches. That broke pretty fast.
He has a Granite Gear (the red one) which is pretty though and roomy. I'd say that's definitely the best one we tried.
The blue one is not resistant at all, but was given to me by someone who lost her dog.
He used to wear one all the time. He's really strong and he wouldn't pull on leash with one when he was younger. It was like it gave him a purpose. He'd calm down as soon as he'd have the backpack on. Then I started using it only when he'd be offleash since it was easier to grab him when it was time to go.
He rarely has one now since he rocks at walking on leash and since he got much better at the chasing game offleash.