I just swapped my winter Marathons for some of the 1.75 Kendas which are pretty much a clone of the stock R20 tyres... I had been running Marathons but installed my old ones on my daughter's Raleigh.

At 45 psi they deliver a plush ride and since my 20 is my short errand bike they work great and really handle our pothole ridden streets.

For $12.00 / each they are a good deal.

I run Marathons on my P20 because it goes farther and faster although you do sacrifice a little ride comfort.