Sunshine Kids Radians-made of re-inforced steel instead of plastic. Eight year expiration vs six years. Taller harness slots and taller shell = longer time RF (Rear Facing) and FF (Foward Facing). Yes, they do have come with their installation issues, but if you let us know what car(s) it will be in we can most likey tell you if it will work or not. RFs to 40lbs now instead of 35lbs also FFs to 65lbs with top harness slots approx 18" in all models. Can be teathered RFing as well.
First Years True Fit-RFs to 35lbs, taller shell and taller harness slots, FFs to 65lbs. New version has an ARB (Anti-Rebound Bar) which has improved some of the harness adjuster issues some were having. Seven year expiration on it vs six years.
Evenflo Triumph Advance-RFs to 35lbs, FFs to 50lbs, harness slots comparable to True Fit (Approx 17"), knob adjusters instead of pull-adjust. Infinite harness system-no rethreading (True Fit also has this feature).
Graco My Ride-RFs to 40lbs, FFs to 65lbs. Fairly new seat but a lot of mom's around here have them, so they can offer their personal experince with them. The shell is comparable to the Britax convertibles but how it is shaped it offers for more RF time. My son fell in
with it at Target the other day. He had outgrown it though due to his long torso (haven't measured recently, but I know he has grown) and still wanted to bring it home with us.
These are in no particular order, just remeber children tend to outgrow ALL seats in height before weight, so something with taller harness slots is always a good thing.