
If you're looking for a seat that will last you through many stages of your child's growth, then you'll want to check out Graco's Nautilus 3-in-1 seat.
It has a 5 point harness that fits little ones from 20 pounds (and one year old) up to 65 pounds. If your child needs to move out of the harness before then, it converts to a high-back booster for children 30-100 pounds. And at the end of the booster phase of your child's life it converts again to a backless booster for children 40- 100 pounds.

The Nautilus has solid construction and is very heavy (so you're not going to want to cart this one through an airport as a 5-point-harness seat, but it would definitely be fine as a backless booster to cart around).
It's about the same size as the Britax Frontier seat in width and height. Though all are bulkier than the SafeGuard Go Hybrid Booster.
This seat includes great extras like wide armrests that allow smaller children to use them and has little secret storage compartments in them where tots can store a little toy or their pacifier. My 1.5 year old loves that feature and so do I because I don't have to find them for her all of the time. There's also an easy to reach cupholder in one of the armrests.
The seat fit my 3 year old and 1.5 year old both well. It is a seat that grows nicely with a child. It has lots of head and side support and is a nice looking seat to boot.

On the negatives, I don't really like that the top latch to secure the top of the car seat to the car has only one strap that goes directly over the top of the car's headrest. It didn't seem to be as secure as some other seats I tried with double straps because of this, though it is secure enough for me to use without worry on trips around town as well as road trips several hours down the road and back. I feel like my daughters are both safe riding in it.
If you have any other questions you want to know about this seat or any other booster I've featured, please leave a comment below and I will answer your questions as soon as possible. I know how hard it is to select the right seat and you always have a lot of questions when deciding to make this big purchase.