Late to the party but..
Here's my entirely personal opinion/experience with Linux Enterprise support for the last nearly20 years now (started supporting linux in house in the early 2000s), we were a 99% Solaris house (a few HP-UX) until even our ISVs were saying that everything they were doing was going linux on x86 (then x86_64) as SPARC was quickly falling behind (yet still cost insanely more $).
RedHat: Was SUPER expensive when it first went RHEL. They initially wanted something like $1600/server/year for x86_64 hosts, set based on what MS was asking at the time. They refused to work with us to split up licensing hosts vs paying for support. Granted, I later learned that our rep at the time was a bit of a jerk and it was probably more him vs the company. Everyone I know that uses RHEL in house, pays for a few critical boxes, runs most on the equiv CentOS to save a ton of $. They are stable and do regular releases though.
Ubuntu/Canonical: FAR more interested in being bleeding edge than stable. Is beloved by SW devs, is way too bleeding edge for HW dev use/compute (I support IC design engineers and the ISVs are SUPER slow at adopting releases so Ubuntu is WAY too fast.. they have a hard time keeping up with RHEL/SLES). They're terrible at outputting patches for things like the automounter, often being years (yes, really) behind.
SUSE/SLES: We started working with them right when Novell bought them and they wanted a foot in the door. They were very willing to split up the cost to license running on hosts/CPUs vs paying for support, which made them far more affordable. They go out of their way to help us work with the ISVs whenever possible. The support response times and quality is fantastic (I have a few co-workers who's dealt with all 3 "enterprise" support channels and they all say SUSE is the best, by far).
Honestly RHEL and SUSE are pretty close as far as stability and sticking to release schedules and all, but my own experience has put SUSE on a level above RHEL overall. Sadly I think RH has coasted far too long on the continued belief that "RHEL is _the_ enterprise linux distro that everyone supports." SUSE was the scrappy competition for quite awhile there and had to really fight to stand out and make a bigger name for themselves. I know of at least one massive chip maker that is nearly completely SUSE in house aside from our IC compute farm, but we have this interesting mix where it's:
IC Engineering compute: SLES
SW devs: Ubuntu
Everyone else/corp: CentOS/RHEL