Hi K.,
I personally love my Britax Decathlon (supports form 5lbs to 65lbs). I like it better than other Britax carseats because you have push a button to release the belt compared to some others where it's a tab you pull or push. I know some kids who can pull on the tab and lean forward and get themselves loose. So that depends on how "curious" your child is.
What I love about Britax carseats in general are it's very easy to adjust so if your kid wears a jacket one day and t-shirt the next day, it's easy to get him in and out. Also if you ever have to move the carseat from one car to another it's super easy to install.
If you could keep your child rear facing as long as possible it's best. I know they say 1 year old and at least 21lbs to face him forward but I kept my son facing backwards until he was 25lbs and 18 months, at which point he didn't want to face backwards.
One last recommendation is to buy is locally and install it in your car. Make sure that you could still out of your rearview mirror. Birtax carseats tend to be large and I have read some peopl complaining that they can't see because the carseat gets in the way.
You will use this carseat for at least 4 to 5 years so it's good to get the one you like and that's rated safe for the child. Every carseat has an expiration date as well (but I think it's long like 7 years) due to plastic degradation.
Good luck finding one!