I always suggest to parents about to purchase a new seat to consider one that has a heigher weight limit on it, and the Britax Marathon is a great seat. Its rear facing to 33lbs, and reclines PERFECTLY! It forward faces 22-65lbs! Most convertible seats have a weight limit of only 40lbs, and many have extremely low top harness slots (14 inches) so its outgrown by height long before weight ,and long before a child should be in a belted booster seat.
So my vote goes to the Britax Marathon. Rear facing to 33lbs, and forward facing to 65lbs!