I've only noticed one: the ability to do less. Along with its excellent improvements over the years, it also gained some staggering RAM usage.
It used to be really nice for self-hosting your own private GitHub alternative on a little VPS or RasPi, but those days are apparently behind us.
Being able to comfortably host a limited version of GitLab for a small team on the lowest tier of Digital Ocean or EC2 instances (<512MB) would be a game changer in terms of the accessibility of GitLab as a product. It would give you access to the long tail of potential privacy-conscious users who would like to avoid hosting their code on a SaaS service (and thus wouldn't be already captured by the market leader, GitHub), but might be put off by the high operational costs involved with self-hosting a GitLab instance compared to some of the lighter weight alternatives.
It's entirely possible that a single Puma process may end up using more memory than a single Unicorn process, so the only way to know for certain is to measure the difference.
As listed in https://docs.gitlab.com/ce/install/requirements.html the minimum is 1GB "1GB RAM + 3GB of swap is the absolute minimum but we strongly advise against this amount of memory. See the unicorn worker section below for more advice."
Most of the memory for the configuration of 4GB we recommend is to run extra unicorn workers https://docs.gitlab.com/ce/install/requirements.html#unicorn... You would save this memory because you can multithread one worker.
It doesn't have a pretty interface, but it works, and its requirements are minimal. I've had good success using it to host student repos in my classes for about 4 years.
Gogs is fine.
People, for whatever reason, think devs have to continue adding more and more features otherwise they see the project as "dead". It's not.
In my opinion the Gitea folks are creating a bloated version of Gogs. YMMV.
He was also totally ok with the fork to gitea.
Gitea exists so that more features can be added faster, not necessarily keeping the code quality ideal.
For many more features I use gitlab. With gogs I'm looking for simplicity.