It is definitely easier to fold a piece like B with the even ends!
I usually keep the "ends" like on A or C attached to the main piece, too. If the piece has a really long tail - like two yards by six inches - I have an argument with myself as to whether I should lop it off to make the piece easier to handle - or leave it on - just in case I might need a really long strip for something.
When my Mom had a garage sale ages ago, her thought was that people would prefer a piece with a straight edge like B, because then it would look more like an unused piece of fabric than a piece of scrap - even if the piece was several yards long.
I do agree with her - as far as "looking better" - my choices would be B first, and then A. But if I was buying I would go for C with the most area for the same amount of money.
Do any of you remember rolling up the scrap pieces (especially from garment sewing) and saving even the tiniest scraps that were left over?