I've been looking to buy these bindings for some time.
I was going to buy a pair on sale (found some for $175!) and then get the ladders replaced when I'm in Whistler (I live in Aus) but unfortunately my boot size is smack bang in between the medium and large binding size (size 10).
I haven't bought boots yet either so I'm playing it safe and buying the 2013/14 season model that fits with the boots I end up buying.
Unfortunately it means I'll be paying a lot more but thats better than finding my new boots won't fit into the binding or are too loose.
Buy the medium size. The straps have tons of extra length and will easily take a size 10 wide boot.
I've got size 8.5 boots and have so much excess; I'm thinking of using a dremel to shorten the ladder and give it a finished look.