I am part of the Bitbucket team. Would love to hear what made you switch from Bitbucket?
I'm not going to lie and this is going to sound kinda shallow but I thought GitLab looked nicer too. Granted this wasn't the main thing that made me move but it did help nudge me a little.
Beyond that it's not like git is very different between places so it's kinda hard to differentiate in my opinion.