So you are looking at a booster seat, right?
My feeling with booster seats, (and truly I haven't looked in to them for a long time) is that how they are built is a little less important then car seats, because they rely on your vehicle's restraint system to protect your child (whereas a car seat provides it's own restraint system). All the booster seat really does is position your child up higher so that the seat belt will lay across their shoulders and hit at their waist correctly.
With that in mind, I would simply evaluate them for comfort and convienence. Many booster seats seem to be rock hard, so keep that in mind if you are a family who takes long trips. Both of my booster seats have backs to them and also cup holders. We do a lot of interstate driving, so I wanted to make sure that the kids were comfortable in them. Beyond that, I would look for durability - I would not buy the cheapest seat on the market, even though I have heard that there isn't much difference safety-wise between the less expensive ones and the pricey ones. The reason I would go higher quality is because your child is going to be using it for a long time. In our state, kids have to be in a booster seat until they are 4 feet 9 inches tall. My third grader is still over three inches away from that, so I'm thinking unless there is a major growth spurt, he'll be in a booster until sometime in the fifth grade.
The other thing to consider is whether you'll be moving the booster seat around alot. I'm finding that as the kids get older, I am putting their booster seats in to other people's cars more often. They might go to the movies with a friend and friend's mom is driving, or they might get picked up for soccer practice - that sort of thing. So think about how easy the booster seat is to move from car to car. Even though mine are full size, they are pretty easy to move.
Anyhow, I hope some of this helps. Good luck in your search.
My DS is almost 4 1/2 and I still have him harnessed in a Britax Regent (goes to 80 lbs harnessed) in my car and a Sunshine Kids Radian65 (goes to 65lbs harnessed)
The Radian 65 was one of the ones I was considering.
Yes the Radian65 does recline and also you could put him RF still if you wanted as it RF's to 33 lbs.