From someone who's day job it is to manage thousands of Linux servers and has professionally worked with SLES, RHEL, Fedora, Debian, Ubuntu, and a custom Linux from Scratch internal Linux distribution, you couldn't be farther from reality if you tried.

"""Due to the success of Ubuntu you have users/experts in small to medium sized companies that have 'given Linux a go' and got some good experience of Ubuntu""". I'm sorry, but there are very few Linux professionals I've ever met I'd consider themselves "experts" who would recommend Ubuntu for their environment. Pretty much 0 except the one guy I work with on the board of Software in the Public Interest (nonprofit that runs Debian). Ubuntu did the smart thing and got onto the "cloud" bandwagon very early. As a result, Ubuntu is likely one of the more pervasive operating systems within that community. The cloud environment is a very small part of the entire Linux ecosystem and doesn't equate at _all_ with the high end "enterprise/hpc" industry. Don't believe me? Take a look yourself at the top 500 supercomputer breakdown by operating system. Exactly 0 Ubuntu clusters. Ubuntu with high end sans such as EMC/Hitachi/etc? Nope, it plays massive second fiddle to RHEL where those companies first certify their hardware for.

Ubuntu is better than Debian regarding security (almost exclusively from the excellent work of Kees Cook, who now works on security for the ChromeOS project at google and hardens the Linux kernel. However, it still can't hold a candle to the proactive security features of RHEL (and hence the awful cheapskate CentOS as you call it). Don't believe me? Look up the gcc stack smashing protector and fortify source patches. Look at the glibc canary code that also helps (in tandem with the gcc patches) to prevent buffer overflows, execshield (from Ingo Molnar, a redhat employee) before NX bits on cpus were super common, the first mainstream distribution of Linux to include a mandatory access control framework (SELinux) enabled by default. Are some of these features in Ubuntu now? Sure. Why? Because Redhat employees wrote them and got them into upstream software, which downstream distributions like Ubuntu which do precious little engineering have adopted.

CentOS is more enterprisey than Ubuntu. Why? Because it is based on the enterprise standard when it comes to Linux, Redhat Enterprise Linux. Ubuntu still sucks with big enterprise SAN gear, it also sucks with some of the more high end networking kit (infiniband on Ubuntu, possible, but a royal PITA and the vendors laugh at you), it is terrible for realtime stuff, but it is fantastic if you want the same interface on your desktop, tablet, and phone. If you don't know your way around Linux (your comment about not knowing your way around Redhat), perhaps you shouldn't be managing Linux servers and you're helping contribute to the list of botnet nodes due to not having a clue what you're doing? Again, I work on Linux fulltime and have for awhile, the major serious differences between Redhat and Ubuntu/Debian:

- /etc/network/interfaces vs /etc/sysconfig/network-scripts/ifcfg-*

- /etc/default vs /etc/sysconfig

- metapackages for everything vs yum groups

- dpkg/apt vs rpm/yum

- Building debs vs building rpms (I could rant for a day on how much ridiculously easier it is to build redhat packages)

- Preseed vs Kickstart (wth was Ian Murdoch thinking here? Preseed is still years behind kickstart in being awesome)

If you know Linux, you can learn those differences well in less than a week. Linux isn't obvious, it requires a lot of reading and experience. My whole point is basically that you are completely wrong and quite clearly don't realize you are wrong because you don't seem to have an idea of what you're even talking about. I do personally think Mark Shuttleworth and the Canonical crew are doing wonderful things for desktop Linux, and general Linux marketing, but they've done tons less when it comes to Linux engineering compared to what Redhat has done.

Sorry for the rant. It isn't normally my style, but this is just ridiculous. Feel free to downvote this, but please do some reading and learn Linux. You'll realize I'm likely right.