Joe,
Remember its not so much the size block as the size of the fabric to be cut. I find it much easier to layout my fabric on the larger mats so I can strip cut. I don't like to cut through more than 2-4 layers at once, as a waviness can occur in your strips. My board, I believe, is 24 x36. I do have smaller ones that I used when I belonged to a guild, once I already strip cut the fabric though.
Does this make sense?