Nicole, I have the Britax marathon car seat. I got it with my oldest(AH)
daughter. The reason I chose this brand is because I heard from my sister-in-law
that it is the only carseat that is tested for side impact in car crashes(at the
time. I don't know about today. I thought that was important because of the
placement of the seat in the car. I've haven't used any other seats but I know
that some have a reclining feature like the Britax that is important for comfort
and to help our kids with their heavy heads not falling forward. Hope this helps

Laura mom to Audrey(5 AH) and Nate(18mo achon)