i think this question should be stickied or new article about this topic written by some expert. I see this question keep coming and coming. There will always be newbies wanting to know about this "best OS" question.
I have been using CentOS 4.x on 2 servers now for over 6 months, and it has been very stable for me. I do agree partly with OCX, you do need to reguarly perform basic maintainence on your server, in order to keep it running smooth.