Pair the 35mm version with the 35mm Tannus inserts. You get the best of both worlds. Supple ride with flat protection.
Took me about 3 days to mount the tire w/ the insert. Not for the feint of heart.
Worth it though because the Schwalbe Marathon Plus is the only 700c tire that can withstand Goat's head thorns out of the box. But those tires are hard as a rock and slippery in the rain.
If you don't have Goat's head thorns then don't worry about inserts