Gitlab package includes too many things! I remember Gitlab sponsors a guy to do proper packaging to include Gitlab in debian last year, not sure what is the status.
I installed Ubuntu MacBook Pro 2015, without any modification they get like 1-2 hours battery life, with powertop/TLP installed it can last for 4-5 hours. Stock macOS lasts 9-10 hours for me.
My friend is using a Dell XPS 13 2016 4K running Ubuntu 16.04 and have no big issue. Beware that while Ubuntu (Unity) itself support scaling and works fine with 4K, many applications (especially, the old ones) are unusable with HiDPI.