2. Heavy: I suppose they are a few mg heavier than others, but I did not notice.
A few mg? The Marathon Plus series weigh more than twice what some other touring suitable tires weigh. In the size you mention they are just under 2 pounds a piece. Also they have a very dead feeling ride that is at least partly due to the stiff sidewalls.
They are very flat resistant though, so if flat resistance at all costs trumps ride feel and very a significant weight difference they may suit you. I rode on a set for a few hundred miles and hated them enough to take them off.
Personally I would pick a lighter tire from their line. I don't have much experience with their other models so I won't recommend a specific one.
I fully agree on that reply. I have been using the Plus tires ... once ... and will never do it again. If I had to commute 2 mi through glass debris, nails etc I would probably choose them. But for touring: Never. Unless you like the additional exercise by the rolling friction.