By half a sheet, I mean the workspace is like a piece of printer paper folded in half. The average piece of printer paper is 12' by 9' or something, the Medium's workspace is 8' by 5' which is not a full sheet. The small is 5' by 3', which is about twice the size of my trackpad. Do not want.
NINJA EDIT: Ok, after seeing Snaffle's pic, I think I'm still going with the Medium. Thanks, Blockland community!