I have a Radian R100 and a roundabout 55 for our 17mo DS (22lbs, 32") in a 2004 Camry, rear facing. The Roundabout is light, compact, and easy to install. The Radian feels much more sturdy and is heavier. It reclines more, but this helps with DS slumping forward when asleep. The install wasn't as easy as the roundabout but wasn't that difficult overall.
Sarah (25), SAHM to sweet little J (7/11) & L (7/13)
, married to my highschool sweetheart
"But I am not ashamed, for I know whom I have believed, and I am convinced that He is able to guard until that Day what has been entrusted to me"