The biggest thing I think would encourage more projects to move is improving discoverability. On Github, I can very easily search for new projects to contribute to, and their Explore page [1] is very nice. Gitlab's, on the other hand, doesn't seem to have a way to browse by category like Github.
For everything else, I like Gitlab a lot -- it seems to have the best integration of tools of any code host.
I completely agree. Actually, I think Github could do a better job with discovery too. The Explore page is a decent start, but why don't I get personalized recommendations for new projects?
Yes, that would be nice -- look at the languages my code is written in or the categories my code is, it makes sense to suggest new projects based on that.
For everything else, I like Gitlab a lot -- it seems to have the best integration of tools of any code host.
[1]: https://github.com/explore