I think it depends how you wear squares generally -- if you like an ordinary puff, the 13" silk is fine, just shove it in points down and you're off. No trouble with bulk. If you like more complicated folds they're too small, though -- e.g. if you want both center and points sticking out of your pocket. The 17" are great for that, though.
17" wool-silk could be too bulky -- the Drake's Unicorn Hunt squares are around that size and verge on problematic for me.
17" wool-silk could be too bulky -- the Drake's Unicorn Hunt squares are around that size and verge on problematic for me.