If you are going to buy really large, I'd get a self-healing type mat. I will go further and say that I see a lot of places that use two of the large green Olfa mats side by side. For me, that is kind of self-defeating. I want a dark mat for light material and a light mat for dark. I can't tell you how many times I have miscut when the light is not correct (even with the OTT light). I now have a sign in my sewing room that says do not cut at night. The shadows are just not good for the dark mat.
My advice, is to get two mats, one light and one dark. I haven't heard of any self-healing ones except Olfa. So anyone's suggestions would be really welcome. I really wasn't looking forward to getting that pink one that I saw online (I'm really not the pink kind).