This site used to run off Ubuntu Server, but that recently changed when I decided to try Debian.
Debian is considerably faster than Ubuntu, and you can feel the difference. On Ubuntu, bash used to be really slow whenever my VPS got busy, Debian stays faster as the OS itself needs less resources to run. That also allows Debian to handle more processes with less resources.
APT and .DEB
Migrating from Ubuntu to Debian was fairly simple. Since Ubuntu is based off Debian, much of what I was used to stayed the same. I can install packages via apt, and install things like OpenVPN 2.4 from .deb files from various online sources. I could have chosen to switch to CentOS or a BSD OS, but I decided to go with what I’m familiar with.
Debian is more focused on having everything open source. On Ubuntu, it’s fairly simple to download programs that aren’t open source, such as drivers. Debian, on the other hand, makes it harder to download programs that are not open source. You need to get each package by itself, or add a repository. Since I like things open source, I prefer that whatever I install with APT is licensed under GPL(or a similar license).
What I miss about Ubuntu
The biggest thing I miss about Ubuntu is canonical-livepatch. The free livepatch solution made by canonical themselves was amazing, and meant I never had to reboot. I can still install snap on Debian, but canonical-livepatch is only supported on Ubuntu. I also miss the community of Ubuntu: there’s no Ask Debian site, and I liked the Ask Ubuntu community. There is still a very big Debian community, but it will take time to adjust.
Let me know which OS you prefer in the comments(for servers, my Laptops and Desktops still run Ubuntu for now)