Personally, I would go with the XL. I think it's better to have some extra room if necessary. If you go with the L, you may run into fit issues if you ever change your boots. Best option is to put your boot into both of them and see what fits best if you can.
Running a size 12 myself and got the larges b/c my local shop had them in stock, but have to really yank my boot out of the heelcup, would go for the XL's if I were you.
Edit: it's not too bad, but if I am trying to unstrap while still moving heading to the lift, it can be a bit of a pain in the ass. Otherwise I love the Capos.
Had the exact same problem with the Meastro's I bought this year. Only had the mediums in stock and my size 9.5 was getting stuck in the heel cup.. Was extremely annoying to say the least and over long periods would cause a pinch point. Definitely save yourself the hassle and get the bigger size.