LINUX

[0]

Which is better in you opinion?

Ubuntu
CentOS

[2]

Ubuntu
CentOS
Debian
Fedora

[0]

Ubuntu, desktop or server does not matter

[35]

Ubuntu with the XFCE desktop environment (DE), referred to as Xubuntu. XFCE is a very lightweight and highly customizable desktop environment, as opposed to KDE,Gnome, Unity, MATE, etc., which can be bloated and slow.

You should always try to get the LTS (long term support) version of any linux distro you're going to use, LTS releases normally come with 5 years of updating, whereas other versions do not. CentOS is also a solid choice, but I've been using Xubuntu for over a decade and have found it to be the most stable DE, with Unity being the least stable.

[1]

Ubuntu with Unity (There are some bugs, but it's better than Gnome)

[5]

Which is better in you opinion?

Ubuntu
CentOS

These are different things. Ubuntu as you mention it is desktop OS, centOS is server grade. Ubuntu server/CentOS would be a better comparison, while you could compare Ubuntu with RHEL/Mandriva/Fedora/Suse etc

I prefer apt, therefore I prefer Ubuntu, even for the server. CentOS does have 10years of support though, compared to 5 years for Ubuntu Server LTS.

[0]

Linux mint mate (if you prefer older look easy to use)
Ubuntu
Centos (if you dont like apt)