GitLab CEO here, we did some informal performance testing comparing GitLab and Gogs and we could not find a big difference in most operations. The only thing that was slow was the web-editor and everything else to do with satellites, we'll remove satellites from the web-editor in 7.13 and will work to completely remove them from GitLab. What speed difference stood out for you?
Thanks! When @lunny finishes the outstand pull request feature it should be a real alternative as it is damn lightweight. There are already plans to im prove the UI as well :)