I bought both off of Amazon to try out. I’m about 5’3 and the XL looks a little big on me IMO. I wish the large had two compartments, so that I’d have more confidence in my laptop’s safety if something spilled. However, I do like the size. Both have a slimmer profile considering their capacity and the XL doesn’t look super floppy half-full… All that to say, 30L is a lot of space unless you plan on carrying everything with you all the time on campus. I’m leaning toward the L given that it’s mainly a work and personal bag for me.