In my country (Denmark), most enterprise runs Redhat, but my personal opinion is that Suse would make more sense after the IBM purchase, especially for public sector usage.
IBM is my first employer and while my inside impression has been great, I'm wondering what the danish view from outside is!
That’s not what I meant though, IBM is an American company, that holds inherent problems for the European public sector. Basically I think we should bet on our own, because recent years have shown us that we may not always have a great political relationship with the US. I think it’s highly unlikely that we’ll have a bad relationship with the US, but it’s a risk assessment we need to think about when we enter into multi-million or billion dollar decade long contracts.
IBM happily helped Hitler plan the Holocaust during World War II. Not even war could stop them from making a buck, so I doubt Trump's shenanigans would.
Indeed, I think that RedHat & SuSe are very similar in their ideas and in their usage patterns. Both contribute quite a bit to upstream projects (there is a lot of work being done on CNCF-stuff in both places, both are RPM-based and both offer a number of different "tracks" depending on your needs). openSUSE also has been very good at keeping up with things that are in development.
On the desktop-side, I think openSUSE is actually nicer, since they officially support a myriad of DEs (notably both Gnome and KDE).
For what it's worth, I use (and have been) using openSUSE both on my work laptop and my private laptop as my daily driver, and I use openSUSE on various private projects as a server OS, though I'm using CentOS 7 at work for all our servers because some of the software we use only supports Ubuntu LTS and CentOS (because the vendor is incapable of building non-idiotic RPMs/DEBs...).
For years, Suse was the de-facto reference implementation of KDE, where it was the primary desktop. I believe this changed after the Novell acquisition (but it’s been so long, I might misremember), and KDE had to find other ways to get an equivalent “showcase” distro.
Unfortunately, that legacy remains with us today, and SUSE is not very friendly to KDE for the enterprise, which I think is really a shame.
Suse has SLES and IBM has RHEL. I am not in the position to compare them.
The non-paid variants are OpenSUSE vs. CentOS. One big difference there is the support life. CentOS 6 with an ancient 2.6.32 kernel and upstart came out 2011 and is still supported. OpenSUSE releases are supported ~ 1.5 years. There are different opinions whether upgrading from one OpenSUSE release to the next one should be done or not. I typically prefer new installations because they result in cleaner systems. But I also upgraded once an it was painless.
LEAP is exactly the same package versions as in the newest SLES I believe. I would expect them often to be a bit older package versions than Fedora, but I haven't compared recently.
Tumbleweed is a leading/bleeding edge rolling release distro. The closest equivalent is Fedora Rawhide.