Is there a site I can go look at that will compare these, and let me decide which one is best for us? Up until today, I didn't even know there was more than one model. I need two of them, to fit in a three-across situation, for my twins, and they need to fit next to DD1's Turbobooster. I think I need them to be 18 inches or less in width, at the widest point, and I need high harness slots because I grow tall kids. I'm looking at the Radian for a combination of narrowness, and the ability to keep a taller than average kid harnessed as long as possible.