OS and Freeradius

Hello, I have a server with freeradius v1.x I took a test server to test an OS update with a new version of freeradius. The stable version of freeradius is 2.2.5? What OS do you recommend? Ubuntu 14.04 LTS or Debian 7? 32 or 64 bit? Is it more difficult to move from version 1 to version 2.2.5? I use Freeradius to a Hotspot system. I Wi-Fi routers with integrated Chillispot (dd-wrt) and routers are connected to the box of customers Kind regards