Initially bought low pile but the wheels made divots in the mat that where tough to move chair out of. The medium is thicker and firmer and holds up to long gaming sessions. I put the medium close to desk and the low behind the medium and now can roll from desk to get stuff off the bookcase on other side of room.
I use this item under my art table on a carpet floor. Don't have to worry about spills (Like ink paint etc) easy to see the mess and easy to clean up. The best thing is NO damage to the carpet.