I'm trying to decide between the Britax Frontier and Britax Marathon for my 25 month old who weighs 28lbs. He already has the Marathon and it is a great seat but I was going to pass it on to his younger brother. So I'm trying to decide if I should get another Marathon or put our two year old in the Frontier. The Frontier just seems so big and intimidating for such a little guy. Any thoughts? Thanks so much!