I have an 06 Jeep Grand Cherokee and my husband has an 03 Volvo S60 and we are looking at the decathalon,
roundabout, or
marathon. The
Roundabout has a good review on Consumer Reports. I'm just wondering if any of these seats will fit in the Volvo's very small back seat. My daughter is just about 28 inches and maybe 17 lbs. She just turned 7 months. I'm assuming fit won't be too much of an issue in my jeep? But maybe I'm wrong. I'd love some insight from all the pros here

We will be buying two seats.
What exactly are the differences between these seats? Anything but size??
Is there another seat someone would recommend? I'm a very nervous driver and want
dd to be extremely safe....but don't we all?
Thanks!