The lady who taught me to quilt told me to buy a green mat - no other. I don't know the difference in quality of others, because I followed her instructions and bought a green mat (Olfa) and have never bought another one. It's holding up perfectly and I've had it about 7 years. The only time it shows any cut line is when I have cut something linty and have jammed fabric lint into the cut but a brushing with one of those body scrub thingys (thanks to a tip on here) and it's good as new. I don't use anything except a rotary cutter on my mat.
Also - these mats regularly go on half-price at the discount fabric shops around here, so it wasn't even expensive.