If you have longer toes, like I kind of do, it helps if the baseplate extends out underneath them so you can apply forward leverage more easily when going toe side.
In other words, try the Large, strap in, and see how it feels when transferring edges on a carpeted floor. If it's easier, go with them.
If not, go back to the Mediums.
Having bindings the right length also helps to distribute pressure across the board, meaning it will feel better under the pressure of the bindings. It's harder to roll over an edge of the baseplate is further away from it. I know this from also having bindings that were too short. They may feel ok at home, but trust me, after riding in them for hours it made my feet feel much more strained than the bigger ones I have now.
Last edited by Gdog42; 12-18-2012 at 04:50 PM.