Fedora vs CentOS -- php/apache and Drupal 7

[Roger]

This is a call for understanding because of lack of knowledge. Apologies 
for the mix of issues in one message but they all relate to the same 
problem.
Firstly,
I've been reading the pro's and con's of RHEL and Fedora and am none the 
wiser. It seems to be around cost of service and lack or availability 
thereof. The beginning discussion was, I think on stability.

It made me start thinking about Fedora vs CentOS because of the problems 
I'm experiencing with Drupal 7 and php/Apache in Fedora 18 so here goes.

I believe that the latest Apache updates of some time ago were flawed or 
do not correctly  interact with php or php updates were flawed and have 
not been corrected. I have nothing to back up this assertion other than 
the problems now being experienced and a recommendation to remove php 
5.4 and revert to an earlier version.
Please don't quote me on this, It's what I've noticed, read and considered.

When I use Ruby on Rails I do not have issues because it uses WEBrick.

Discussion to date says that CentOS circa 6.n has the Fedora 14 kernel, 
is rock solid and gets updates every 6 months approx.
Fedora 18 has kernel updates every few days or weeks at most. Frankly I 
enjoy the update cycle. It's interesting to see what gets improved. I 
have always run latest Fedora versions and have not experienced the 
current raft of problems.

Fedora 18 sudo yum update, updates everything apps, modules, etc that 
needs security fixes or improvements.

CentOS is a server system but can be used for a stable desktop system 
and has been recommended as an alternative.
So what does CentOS 6.n desktop, yum update actually update or does it 
leave all the apps like cinnamon desktop, skype, gimp, apache, php, 
libreoffice, python, pulseaudio, gnome, Firefox or chrome as they are 
first installed, circa Fedora 14ish?
One would think that this would leave significant vulnerability.
If it runs the latest spate of updates then is it not little different 
from Fedora 18 but with an old kernel?

Further reading implies that the better CentOS installation should be 
text based as a server only and that I should run all my work on the 
server not Fedora 18.

I am now having significant problems with an already built Drupal 7 site 
on Fedora 18 after the latest spate of php updates and am perplexed as 
to what to do to get a quality stable functioning and stay functioning.
  I've got ubuntu 12.10 but it is now so slow that it's not easy to use.

Further, I have 2 gig memory, intel mb, fast dual cpu, 250g hard drives 
and my desktop fedora 18 uses 55-63 percent memory. I thought this may 
be affecting php and apache, hence Drupal, but
The Dell 1520 laptop has the same internals and memory and uses 
25percent of the 2 gig memory, same drupal, same Ruby on Rails.
I'm puzzled because after checking ps aux, top, and System Monitor on 
both they are very similar yet memory usage is markedly different. I do 
not know what I should be looking at to understand the issues and/or fixes.

Is there an app that I can use to track what happens in the browser, 
apache, php and Drupal when I start the Drupal site on my machine.
Help is greatly appreciated
thanks in advance
Roger
Off Topic...Does anyone know of a Rails dev who would be able to help 
and teach me building a small application?
Thanks again
Roger