Just to offer a different perspective, I've run both Marathons and a Marathon Plus and didn't like them one bit. They're incredibly flat resistant and long-wearing but as a result super stiff and not very grippy (not that you'll be railing corneers, but it matters when wet). I had to air mine down to 40 psi to get any semblance of IMO acceptable ride quality, otherwise they were like rolling on solid rubber.
I'm a big fan of Conti Gatorskins and Specialized Armadillos. Flat resistant enough for me (and I do plenty of city riding), and very supple. You do give up a bit of longevity though, since there's not an inch of tread like on the Marathons. I'm about to pull on a pair of Bontrager Hard Case road tires and I expect them to be similar to the Gatorskins across a wider range of price points, but it's too early to give them a recommendation.