Personal preference plays a major role here. The Marathon Plus is very flat resistant and weighs more than double what some suitable tires weigh. The Continental Gatorskin has a nice lively ride and weighs less than half what the plus weighs and is reasonably flat resistant.

I highly value a lively ride and don't mind fixing a flat now and then. So for me the Gatorskin wins by a large margin. If you want to avoid flats at all costs and are not very sensitive to ride characteristics the Plus could be for you.

There are lots of other choices, but those two are pretty representative of the ones folks tend to like.