Depends - If we chose Fedora, we stick with our R300 (We will be asking KC if can have a second one so we don't have to format and so we ge faster transfer speeds for all of the files that would need transferring.). If we go with Windows 2008, we'll still be hoping to have 2 dedis for a couple of days, but the new dedi will be an R210 which has a better CPU (http://ark.intel.com/Compare.aspx?ids=42928,33082, - New one is on the left, Various improvements, slight speed decrease) and Faster RAM (1333mhz as opposed to 667mhz).
Either way I'm going to try for an R210. Also linux won't result in any downtime - the old dedi wouldn't go down until everything is migrated and ready to go. Also I should mention that we don't have to factor in license costs - I have 10 legal enterprise licenses And if by some incredible chance we get an R210 as well as our old dedi, it would be Windows 2008 on the R210 with all our gameservers (and nothing else), and Fedora on the R300 running all our web and miscellaneous shit. And the IPs would be switched round of course.
Technically that would be linux Anyway we'll see what happens on windows first if we get two servers, and it's down to the poll otherwise.