One big thing gitlab has that github doesn't is the ability to download (or clone I think)repositories from a mobile browser without changing to desktop view. Yes there are actual reasons why someone would want to do this.

Maybe I'm blind, but I've scoured the mobile page for a download or clone link and always ended up giving up and switching to desktop view. I just checked again, and couldn't find them after a few minute search. On gitlab, it's immediately visible just above the clone repository link on the main repository page.