LOL I just asked what you were thinking of. My order of these...
First Years True Fit
Radian XT or 65
Evenflo Triumph Advance
Britax Marathon
Britax Roundabout 50
Reasoning being, the True Fit has a super tall shell and lots of leg room, built in lockoffs, is pretty easy to install, has a seven year lifespan, has a great price, very soft and comfy, great weight limits.
The Radian is harder to install, but it has an eight year lifespan, tall shell, a 40 pound rear facing weight limit, lots of leg room.
The EFTA has a tall shell, high top slots (17.5", same as the other two), decent weight limits, pretty easy to install, and is very economically price.
The Marathon and Roundabout 50 don't make my top five, but on your list they'd be on the bottom. The Marathon has the same weight limits as the True Fit, but the shell is shorter, the top slots are lower, there is less leg and shoulder room, and it's far more expensive with a six year lifespan. The Roundabout 50 is about the same size, though it has a 50 pound forward facing limit instead of 65, and it doesn't have built in lockoffs. It's economical (for a Britax),but still, you can get a taller shell, higher weight limits, and a longer lasting seat for less money.
Wendy