The Brompton build a bike site said the more puncture resistant one is 0.162kg heavier. Is this likely to be noticeable? What do you mean by rolling resistance?The Marathon Racer doesn't have bad puncture protection at level 4. Marathon + are highest level 7 PP, but will be a fair bit heavier than the Racer and will have more rolling resistance.
I would stick with the Racer and see how they go.