In my opinion the web UI in gitlab is miles better, the fact that it has a "merge this thing" button makes it a game changer.
Now since we are coming from phabricator you have probably used the
arc patch DXXXcommand to download and locally test a patch.
The gitlab web UI has a a link named "You can merge this merge request manually using the command line" that if pressed tells you to
git fetch "firstname.lastname@example.org:sander/okular.git" "patch-from-kde-bug-415012"
git checkout -b "sander/okular-patch-from-kde-bug-415012" FETCH_HEAD
if you want to locally test https://invent.kde.org/kde/okular/merge_requests/80
That is *horrible*
git mra very simple script that makes it so that you only have to type
git mr 80
P.S: If you're an archlinux user you can get it from AUR https://aur.archlinux.org/packages/git-mr
P.P.S: Unfortunately it does not support pushing, so if you want to push to that mr you'll have to do some work.