I use gitlab because it is free and embodies ethics inline with my own. There has been a conversation that has appeared to be largely one-sided-- developers asking for more features, control, consideration ect; and it github largely seemed to be ignoring these concerns. A large group of popular open source contributors wrote an open letter to github and even then, there was not much change until gitlab responded.

Github is a much larger organization, and it does a lot of good. However, I like gitlab, they are engaged in the community, really love their users (thanks for the tshirts btw!) and they do things like this-- apologise for their mistakes and listen to their users.

So yes, even though they both just copied open source software created by linus torvalds, the great innovation is building a community around that infrastructure, to which I think gitlab is doing a better job at present.