hey ... i v never used anything other than RH/centos/OEL (all same build) n suse (not much diff)..
i found RH/centos/OEL and SuSE seem to be the most widely used ... i v never seen servers running on arch linux or any other distro of linux .... may be bcoz there is very little enterprise level support for these?
What you've said about enterprise support is true. But personally speaking, I love running my LAMP stack on Arch over every other distribution.
how diff is arch linux from the others?
Read these:
*wiki.archlinux.org/index.php/Arch_Linux
*wiki.archlinux.org/index.php/The_Arch_Way
In simple words, Arch is a minimalistic distribution. You only install things which you actually need. You start with command-line and then end up downloading and configuring everything manually. You actually end up having a very fast operating system. Also, Arch is a bleeding-edge rolling release distribution. The packages which you get are always latest unlike Debian which aims for stability.