I love how Netlify allows you to use the benefits of static site technology (like distributed version control) while allowing for dynamic site functionality like forms. I looked at the documentation for forms https://www.netlify.com/docs/form-handling/#receiving-submis... and it looks very easy.
I can see how people would use Netlify over GitLab. By the way, in GitLab we allow you to test a branch with a review app. In fact for 11.5 we're planning to show you a direct link to the page that changes https://gitlab.com/gitlab-org/gitlab-ce/issues/33418 and someone contributed the option to make the static site that is generate with pages private https://gitlab.com/gitlab-org/gitlab-ce/issues/33422