This looks like an old thread, but I have been trying to figure out the “best” ground cloth material too. I made one myself from 1.1 oz/sqyd silnylon from RBTR and really liked it, but sold it with the tent I sized it for (TT double rainbow). While much better than off-the-shelf ground cloths, it still didn’t fold down very small.
I only use a ground cloth when I know I’ll be camping in abrasive environments (like rocky mountaineering “camp sites”), not groomed campground spots. So I may lean more toward durability than some on this site. If I will be camping on soft dirt, I generally don’t use a ground cloth since I use a tarp tent with a floor.
I have tried polycro and hated it. It is about as puncture resistant as a ballon. But the biggest problem is tear strength. Once a rip starts, it tears across the entire sheet with almost no effort.
I think I’ll try the polyethylene (LDPE) painter cloths since they’re so cheap. Maybe I’ll find a thickness that is a good balance for me.