I have had trouble with Fiskar mats warping even though I stored and cared for them correctly. I was looking at some Fiskar ones in JoAnn's and all of them were wavy. I've never had that problem with Olfa. I've had a couple of Olfa mats for over 15 years and they are still going strong. I have never had Martelli but have heard good things about them. Mats are expensive so look for sales, coupons and take good care of them.