Unless you're planning on carrying $120+ worth of groceries every single day, the XL is too big.
I'll post some pictures of my L. It's MASSIVE. I've taken home $100 worth of groceries without any problems. I've carried a sixpack, a jacket, my laptop (with padded sleeve), a set of cranks, handlebars, and a few books with lots of room to spare. It's really a big bag.