Which is better for a server Debian or Ubuntu?

Whichever you are more familiar with. The practical differences are not really significant for most situations.

Ubuntu is generally more prevalent. Mainly because it's got Canonical behind it if you get the support package. Otherwise I'd recommend Debian if you intend to manage it yourself.

Without knowing what you want to do then I guess we can't guess. Blindly between the two I might go with Ubuntu.

I agree with IsaacKuo. It's really which one you feel more comfortable with.

As an aside, are you referring the Ubuntu Server distribution flavor or Ubuntu in general? If Ubuntu in general, I advise going with an LTS.

In general, debian is more "hands-on" and ships stuff the way upstream provides it and expects you to read man pages and figure stuff out,configure stuff the way you want it, etc.

Ubuntu is somewhat preconfigured in what they think you might possibly want.

Even ubuntu server includes snapd, which is an alternative package management system that ubuntu's parent company pushes that some people don't like.

But both of them are fine. You can get commercial support for either one if needed. I'd personally just use Debian, but Ubuntu would work just fine too. They're very very similar, just think of ubuntu as debian configured the way canonical wants, instead of the way the software developers want.

In addition to the previous comments (which I agree with, all of them):
https://www.turnkeylinux.org/ for preconfigured servers (based on Ubuntu)
Furthermore there is (was?) Zentyal server, of which the development edition is free. I can't find any activity after 2021...;-( Latest version (7.0) still works though and can be upgraded from 20.04 to the latest Ubuntu. https://zentyal.com/community/
Or look at https://alternativeto.net/software/z.../?license=free

Again: it all depends on your needs.
- Any modern mainstream GNU/Linux distro will be suited.
- How much effort do you want to put in it.

Last (very personal) recommendation: run your server in a VM. Snapshots... easy deployment...

I would just like to thank all of you who responded yesterday.

I used to use a Debian server for a few years and I switched to Ubuntu LTS a few years ago and i have been very happy with the switch. Debian is more *hands-on* as someone has said in this thread, when something breaks, and it will break you have to go through tons of man pages to figure out what can be done, not so much with Ubuntu which has a plethora of information on boards and forums where people are happy to oblige and help you right away, not so much with the Debian community, they are more *go figure it out on your own*. I also roll my own kernel for the Ubuntu cause I have some peripheral devices which aren't supported by the kernel that comes shipped with the Distro so I have to compile the modules manually into the kernel for it to function properly. Something you can look into if you are using a lot of different add-ons

After all, "Red Hat" predicated their entire business model on subscription-based "support," and they did extremely well as a publicly-traded company. There definitely is a market for providing "turn-key Linux systems" as well as "easy-to-use support" which does not require intensive technical knowledge. Sometimes, "you just want the damned thing to work." (And: "if somebody else has already figured it out, why do I have to do so again?")

Ubuntu (Canonical ...) has taken this approach. If you "do it their way," it definitely works. You can reliably keep a "farm" of servers up-and-running for weeks and months and years with only "routine maintenance," with Canonical undertaking to do most of the work. It's a sound strategy.

A server is either a machine, such as a rack server, or it can be software running on such a machine. So you're either asking "what runs best on server hardware" and there is no clear answer to that except "an OS which supports the hardware" or you're asking "which of those two is better suited as a server OS" - there's no clear answer there either.

As a server OS, it really depends on what your server is going to "serve". When it comes to Debian and Ubuntu, there's little difference. I find that Ubuntu has some extra bling which can get in the way, whereas Debian has a more basic approach. Apart from that though, you have the same package management tools and systemd as standard. You may find that your specific use case is better handled by one or the other. If you know the hardware is supported, it doesn't do much harm to set up a test server, which can be any old box or a VM and just see how everything installs, see how it's configured, take plenty of notes and test the thing before you deploy it.