I am posting the item below not to start any "flame wars" nor to be any 
mythological creature from Middle Earth or anywhere else, but rather to 
put forward what I have found from one "professional" analysis of the 
RHEL situation -- and not an analysis for which I have sufficient data 
to support.  In the article below, the conclusion "push" seems to mean 
that either RHEL clone is the same.  Rather than simply including a URL, 
I am posting the entire article for any later historical archiving -- 
unlike academic journals and articles that exist for posterity, much of 
the commentary of the computer technology areas seems very ephemeral. 
Nonetheless, when RHEL 7 and its clones come about, there may be 
interest in examining the historical commentaries, just as there is in 
discussing any evolving technology (e.g., HEP detectors).  For my 
personal choice for X86-64 systems that need to support 64 bit 
operations, I have switched to SL 6 ; for systems that can live with 
IA-32 operations (e.g., my laptop and other work computers), I am 
staying with CentOS 5.x for now -- when these switch to RHEL 6.x, I 
suspect I will be switching to SL 6 simply because I do not want to 
support multiple environments for production.

 From URL: 
http://lostinopensource.wordpress.com/2011/07/13/the-clone-wars-centos-vs-scientific-linux/

The Clone Wars – CentOS vs. Scientific Linux
2011/07/13 jduncan

With Linux in the Enterprise, RHEL is king. Sure there are people who 
love and use Debian, or Suse. I would imagine that if you looked hard 
enough you could likely find somebody who’s using Slackware or Gentoo in 
a business somewhere. But I think it can safely be said that RHEL is 
currently the dominant enterprise Linux distribution. Then, of course, 
there are the clones.  If you so choose, you can forgo Shadowman’s 
Support team and either compile the freely available Redhat Source RPMs, 
or choose to use a community-supported RHEL clone. Currently, the two 
most popular of those clone distributions are CEntOS (Community 
Enterprise Operating System) and Scientific Linux (SL).

So if you have decided to not utilize Redhat support, which of these 
downstream clones is the better choice? With the recent (much delayed) 
release of CentOS 6.0 in the past week, many companies are looking to 
move up to the RHEL 6.0 family of operating systems. But is CentOS still 
the right choice? Being a primarily CentOS shop, and being more than a 
little OCD myself, I decided to compare the two in as practical as a 
manner as I could. Below are the results.

Maturity:

When it’s running on production, you don’t have time to wait on a tiny 
community to figure out how to backport in some obscure cross-site 
scripting vulnerability in an even more obscure module in your favorite 
language, even if you’re part of that community. An enterprise operating 
system needs to have an active and robust community to support itself, 
paid or not.

CentOS has been around for a long time and has a huge following. There 
have been murmurs of late about the core contributors getting tired, and 
the delay in CentOS 6.0 was the evidence. I don’t believe that fully, 
but I do believe the project could do with some fresh blood and possibly 
some new ideas.  But I don’t think it’s going anywhere anytime soon.

Scientific Linux hasn’t been around nearly as long, at least on the 
scale that it is currently enjoying. The community, however, is vibrant, 
and is backed by several large research labs such as CERN and Fermilab. 
Big plusses.

Advantage: Push

Workflow:

In Open Source software, the process is often times as important as the 
product. While I don’t believe there is anything massively different in 
how these 2 projects are doing what the do, SL is certainly better at 
talking about it and making the community aware of how it’s working. 
This presentation(PDF) is a pretty great one, even if it’s a little 
dated. SL Community, I’d love to see an update, for the record.

Advantage: Scientific Linux

RHEL Compatability:

This used to be a much larger difference, as late as version 5.x. 
Scientific made some pretty large changes to the RHEL repository 
structure, and added in some packages of their own. CentOS has always 
been as faithful a clone as was possible at the time. This is largely 
cleaned up in version 6.0, with the extra SL packages moving out to 
external repos, but much like the workflow advantage above, perception 
is still a strong influence.

Why is this important? Well, like lots of people, we’re a mixed 
RHEL/CentOS shop. It just makes life SO MUCH EASIER.

Advantage: CentOS

Mirror Speed and Availability:

I couldn’t find any perceivable difference in this category. Both 
networks are robust and highly available.

Advantage: Push

Community Support:

This is one of the most important factors when adopting a distribution, 
and sadly the one answer I’m not able to fully answer. I utilize CentOS 
support all the time, via the web, forums, and IRC. I’ve only 
occasionally sought support for SL, and this was way back in version 
5.2. So I’m not really qualified to answer this one fully right now. 
However, I see active forums off of their home page and a 10 minute 
visit to the IRC channel on freenode saw plenty of conversation for a 
Tuesday night. I don’t think SL would have grown so much without good 
community support.

Advantage: Push

Lifecycle Support:

This was the one that surprised me.

As expected, CentOS mirrors the RHEL lifecycles. RHEL/CentOS 5.x will be 
supported through 2014. They haven’t updated their wiki yet, but I’m 
sure 6.x will be the same, with a full 7-year lifecycle.

Scientific only plans on a three year lifecycle. But on their forums 
they also mention supporting things in theory as long as Redhat does. So 
I’m a little confused on this one.

While I don’t typically plan on using the same OS for longer than 3 
years, if it ain’t broke, I’m certainly not fixing it.

Advantage: CentOS

So those are my thoughts on the situation. Scientific Linux is 
definitely on the rise, and CentOS certainly needs to air out themselves 
a little. But at least with version 6.0, we’re still going to be going 
with our tried and true CentOS. I’m just not comfortable enough, yet, 
with the Scientific Linux community, mainly because they still don’t 
quite know how long they plan to keep their products alive. Out of this 
look at RHEL clones, though, the single biggest thing I’ve discovered is 
that I’m going to have to keep evaluating this choice down the road.