We have the
Marathon and love it. We have put it in a Buick Park Ave, Acura Integra, Honda CRV, Subaru Outback, Chevy Silverado and a Chevy Tahoe with little to no trouble. We currently have one in our Tahoe and a second in my husband's Silverado 1/2 ton. The Silverado has a small back seat, its not the crew cab style and while it's tight it does work.
It's pretty easy to switch between vehicles once you know how to install it, but we have two now so we don't have to switch it. I think you have to consider how often you would be switching between vehicles to decide if it will work for you. We would be switching daily if we only had one and that's just not convenient for us. Having two seats for each of our kids is expensive, but it gives us tons of flexibility which is really nice since all three are in daycare/school.