Small vs Medium Stuff Sack

I have several medium stuff sacks which I adore, but I need one in a different color. What I really want is an all fabric medium ultraviolet, but it isn't available. Does anyone have both the small and medium stuff sacks? How does the small compare? I find the medium nicely holds a good size ball of yarn, my needles/project, and my pattern, and I am concerned that the small might be too small. Help? (I know there's an ultraviolet medium with the clear bottom, but I really don't care for the clear bottom.)

I'm currently carting around a small stuff sack with an in progress dishcloth/facecloth. It's on circs. The ball of cotton worsted and the project a small pair of scissors and a couple of stitch markers are all I have in there. I don't have a pattern in there, it's on my iPod Touch, which has it's own home in the Swift. I think I've also had socks in there, but don't remember if it was 1aat or 2. I use circs for socks too.

The small stuff sack will easily hold a single skein (100g) project in progress on circular needles, folded pattern if you use paper, a chibi, tape measure and mini organizer pouch with stitchmarkers. There isn't much room in the bag for anything else though. You can always use the stuff sack for purse/knitting bag organization if you determine it's not large enough for your project. Like with organizer pouches, imho you can never have too many stuff sacks.