I have both an Olfa and a Fiskers 18" x 24". Like them equally well. The Olfa seems to be just a tad thicker, if that matters. As AIMR pointed out, the Fiskers has a reverse side that's light (mine's light gray) to make it easier to cut dark fabrics. I seem to use my small 8" x 11" Omnigrid and my rotating 13" x 13" Fiskers the most though. The Omnigrid cutting mat is on one side and has an ironing surface on the other, then they fold together to make a folder. That's convenient for putting in a tote bag when I'm taking a project with me. I also use it at my machine so I don't have to go to my bigger mats for trimming small things. The rotary mat is what I use when I'm trimming up blocks. It's so much easier and more accurate than moving the block.
Went to JoAnn's to buy some white fabric today. I was only going to buy a yard since the muslin I chose was 108" wide, but there were only 2 2/3 yards left on the bolt, the muslin was on sale, there would be an end-of-bolt discount, plus I had a 20% off my total purchase coupon, so I did what any right-minded quilter would do - I bought it all! I now have the equivalent of approximately 8 yards of 42" wide fabric. Think I'm set for a round or two unless someone gets fancy-schmancy on us and asks for white-on-white or beige. LMAO because I'm probably the one who'll do that!
I almost photographed my half-full waste basket after I finished cutting most of Donniesgirl's blocks because I knew AIMR wouldn't believe me if I admitted to actually throwing away scraps that were big enough for a crumb quilt. For the uninitiated, that means anything at least 3/4" x 3/4". I'm seriously trying not to start a third crumb quilt since I haven't yet finished the other two.