Who's your provider?
If you're getting it from Linode, go with a 32bit OS. I don't think they support Wine on 64bit systems,
as evidenced by Nal's topic further down the page.
If you're not, any of them should work fine. Ubuntu DESKTOP is considered very user friendly, while Ubuntu SERVER (what you're working with) is considered bloated and no real benefit.
CentOS is server software.
I'm not familiar with Fedora, although it is popular, and Scientific Linux is not for your purposes.
I would personally go with CentOS 7, but Ubuntu might give you better support.
I advise you to go with Ubuntu, assuming you're going to be hosting Blockland servers on it.
