My folder with 20" tires came with Kendas on them. Fine, but do get the occasional flat. Replaced the back tire with a Schwalbe Marathon Racer 20x1.5. This tire can inflate up to 85 PSI and is faster. No flats yet in over 5,000kms. I find the tire a little squirmy on corners sometimes.

I also have a folder with 16x2.0 Schwalbe Big Apples. Only go to 75 PSI and feel a little slower. Haven't put huge km's on these yet but they seem fine.

Of the three the Marathon Racer is the favourite.