The top of the head tube is 35mm lower on the size L so that one will allow a bigger drop for you. The stack and reach numbers published for the XL don't jive. I think the actual stack is 597 (vs 585) and the reach is 388 (vs 393). If the geometry numbers given are accurate then either frame can fit you and it comes down to how much drop you want and how much saddle setback you need. You'll end up with a little more setback on the L because the seat tube angle is steeper.