RE: Salesperson tried to talk me out of a Regent and into a MA - questions???
If you want to harness for a long time - say to 8-10 years old, then the Regent is the way to go. They expire in 6 years, so the seat would last to 9-9.5 years for her and then she might be able to go straight to a seatbelt, or just a backless booster.
The Marathon will only get you about 18 months - not much time for the price, but you could always sell it afterward or give it to a friend that needs one. She probably could use a booster afterward, but you may decide at that point that you want to keep her harnessed longer and you will be back to a Regent.
One alternative would be the Radian65. It usually lasts a year or so longer than a Marathon because the top slots are taller. That would be a compromise - harness for another 2.5-3 years and then to a booster. At 31 lbs, you could also look at something like the Recaro Young Sport which would harness to 40 lbs and then become a good booster. Both of these are in the same price range as what you are looking at.
I have never heard someone complain the Regent is "uncomfortable and hard" - big, yes, but it also has a recline bar that you can use if it is too upright.
CPST and Mama to three boys ('03, '05, '07)