I've used Github prior for a long time, and then got attracted to Gitlab for its CI tools and different pricing model that made more sense for our team. But would love to hear others' comments why they are using one git service over another.

What service is the monkey icon for?
I have used these more popular ones:
GitHub: I don't get the popularity of GitHub outside of open source projects since I've usually looked for private repos. It has a good interface. I just wouldn't pay for the private repos if I can get them with the below services.
BitBucket: I like their service. Free repositories and backed by a company that's been around for a while and offers other development services. Not the best UI. The UI is kind of slow but overall easy to understand and navigate.
VisualStudio (VSTS): Also free private repos. Pretty good features, but I find the interface and features to be overkill for me. I've used their CI/CD service with success. UI is sort of what you might expect from Microsoft. They are rolling out a new UI that might be better.
GitLab: Also free private repos. I tried out the CI/CD service and it was easy to set up and worked well. The interface is also the most responsive out of all of these in my opinion.
I think that if I were starting from scratch and wanted hosted private repos I would go with GitLab first then BitBucket or VSTS then GitHub.
Mark
I've tried several. It's mostly for my own and open source projects with up to 10 users. I can't speak for big teams.
So basically for individual developers, I recommend Github.