I've got a Fiskars 24" x 36" and a June Taylor 18" x 24".
I bought them because they were the best priced matt at the time I was getting them. I've had them both for at least 4 or 5 years and both are in excellent shape - no indentations or tears. I'm a casual quilter (not everyday), so I can only speak from that point.
I'd say both of these brands are excellent choices. I've always made sure to have mine laying flat, so they don't warp.