I've used the marathon plus and the Vittoria rando pro. Both are exceptionally flat resistant. I put 3100 miles on my first set of Vittoria's without a single flat, and that is on very rough, glass-strewn city streets. I had no trouble with side wall cuts. I'm on my second set now -- 400 miles in and no flats. I think they ride pretty well too, not cushy, but definitely comfortable. I briefly used a set of Vittoria Voyager Hypers and was amazed at how fast they were, but after six flats in 1600 miles, I ditched them.

The Schwalbe marathon pluses are on my IGH Dutch bike where a flat would be a major pain in the backside! They have about 3000 miles on them and look like new. They don't even show any tread wear. Pumped up to 85 psi they are pretty harsh to ride, but get more comfortable as the pressure falls closer to 70 or lower. I had to take them off once and found them *very* hard to get back on. Once I put the Kool Stop tire bead jack on them, though, they went on okay. They good thing is that you are so unlikely to get a flat and they last so long, that you don't have to worry about installing them too often.