Even though they are all in the "Marathon" line, they are all very different tires.

Marathon is the most basic in this line and we sell more of these than any of the others. Great, long lasting, nice rolling tire with a very effective and thick puncture protection belt. Should last the average rider 7-10k miles.

Marathon Plus is our toughest and most puncture resistant tire. Very thick and very resilient puncture protection belt will virtually eliminate flats. Yeah, you can still puncture it, but generally it will withstand most anything that would puncture a normal bicycle tire. It's certainly heavier, and can be a beast to mount, but once mounted you shouldn't have to fuss with it much.

Marathon Racer is a lighter weight member of the Marathon line. It's puncture protection belt offers decent protection, but the tire is designed with speed in mind, not so much puncture protection. Unlike the other two mentioned so far, the Racer is available in a folding bead, which improves the weight savings significantly. The speedgrip compound is fast rolling and sticky in the corners, but you're not going to get the mileage out of this tire that you would out of the other two.

The Dureme is part of our Evo line of Marathon tires. Lighter weight carcass, rubber compound that is much more sophisticated and technically superior to the regular Marathon line, and a very light weight but tough and effective puncture protection system. These tires have great grip in all conditions (except snow/ice) and yet have the same longevity as the standard Marathons.

Hope this helps.