Interesting comment. I checked with a Union rep a while ago and he recommended the L/XL for my size 10 Fargos. Now, those are bulky boots, but if the M/L supposedly fits size 10-10.5 Kaijus perfectly it should be able to take my Vans, no?
The sizes overlap between 9.5 - 10.5.
Sizing for all bindings is best done in person at your local shred shop.