Alright so I know you don't wanna hear this but you rrrreeeaallyyy should be trying these on bro. Haha. Most people get those things custom fit.
But I'd get the Large for sure. It's going to break in like anything else and from experience I can tell you there is NOTHING more annoying than having knee braces slip down under your snow pants. Especially because if it happens while you're riding it can pinch your skin and shit and if it moves even a little bit sometimes you don't notice until your knee really starts getting sore and THEN you notice your brace is on wrong.
Our father, who art in heaven, freeski be thy name.
Thy kingdom come, powder days be done, on Earth as it is in heaven.
Gives us this day our daily shred, and forgive us our faceplants,
As we forgive those who faceplant against us.
And lead us not into gapers, but deliver us from ski school.
For the kickers, the powder, and the back country yours,
Now and forever, Amen.
No one needs them, they are preventative (to my knowledge), and they are VERY cheap (affordable, good price, w/e). The one I had to use after my surgery was 1400 bucks and it fucking sucked. Luckily I didn't pay a dime. TY ALBERTA HEALTH CARE.