I went with Deuter. I think it was the Comfort 2. I compared them all and tried them on in the store with weight in them. Ended narrowing down my brand and tiers of product. Then found a used one on Craigslist for half price. The guy used it once.
For me I used the same criteria and scrutiny as I would a quality backpack. Designs are pretty similar, so it's more about fit. On the Deuter the hip belt fit better and felt more comfortable with weight in it. The weight was better distributed on my hips with no points of pressure. Very comfortable with30lbs. Osprey was a close second, but the belt was smaller and just a little less comfortable.
Be sure to review tourso length and adjustability. I have a long tourso and this is a factor for me when buying a hunting backpacks. Both Osprey and Dueter fit me well. Ease of adjustability is a factor as well because we're often switching it between my wife and I. Needs to be simple and repeatable, meaning it's easily know where to set it vs relearning each time.
Deuter has adjustable stirrups, which Osprey did't have (at the time). I think these make it more comfortable on the child because it supports their leg weight and allows the legs to sit at 90 degree angle vs hang straight down. Not a factor in short hikes, but feel it could be a factor on longer ones. It's no fun if your child gets uncomfortable and upset when you're miles down a trail. Lastly, I liked the sun shade better on the Deuter....or I should say my wife did. She's crazy about keeping direct sun off my son. The shade looks goofy, but works better than I expected it would. Just the right amount of shade but doesn't obstruct his view or give him much to grab.
In all the brands the middle version seemed the best choice. Right balance of form and function. The top tiers in each brand really had too many pockets, which just means you will carry more crap.
I liked the design of Deuters side loading option. It's a little easier, especially in cold weather when you child might have a few layers on. I also liked the built in mini pillow. If my son gets tired he goes to sleep on it. I realized this after the purchase. I think the Osprey was a little less padded in that area.
Oh, fyi I think it was one of the top end Deuters, where the child sat significantly higher relative to your body. They were almost looking over my head. I didn't like it. Started to feel too top heavy for a pack weight. It worried me since I hike mostly trails with terrain of variable footing. I bring it up because I never would have know this based on pictures or online photos, they all looked identical, but it was obvious when I tried it on.
