I hated the Marathon Plus. It wallowed terribly. I also got punctures, about 2 or 3. The blue stuff on the 1.35" narrow Plus was not enough to deter glass shards. They got through on the edge of the blue strip.
That's a good point about the narrow Plus - my current Marathon Racers are 1.5" so I was considering the 1.35 but in light of your experience, maybe I'm batter off getting the 1.75 (one-sixth wider than current tyre) and hope it'll not interfere with the mudguards.
Thanks for your feedback, much appreciated