I recently switched to Marathon Plus after putting 4000 or so miles on 2 sets of Bontrager Hard Cases. I do prefer the ride on the Marathons. I think because of the extra strip of rubber down the center of the tire that the ride is a little more forgiving over bumps than the hard cases were. I also run the Marathons at a littler lower pressure which also forgives the bumps. I feel a bit better running them at the lower pressure because of the extra protection in the middle.
Installation nearly killed me until I learned how to properly install them. The trick is to push the tire as far as you can into the wheel until you get about halfway around and then start using zip ties to hold the tire in place. I was able to install the second tire in about a minute and without the use of levers. Just look on youtube how to do it. You'll thank yourself later.
Bottom line: I don't regret switching to the Marathon Plus tires. The Bontrager Hard Cases were fine, but the ride on the Marathons is much nicer.