Best Windows Today

[seberle]

I see all the Windows platforms in the product requirements for Mezzmo Server:

"Windows 10 (32-bit and 64-bit), Windows 8 (32-bit and 64-bit), Windows 7 (32-bit and 64-bit), Windows Vista (32-bit and 64-bit), Windows XP (32-bit and 64-bit), Windows Server 2012 R2, Windows Server 2012, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Home Server (WHS)"

Given I am going to stand up a box, which 64-bit Windows OS would you choose today (10/17/2017) from the above?

(edit): From the perspective of Mezzmo not a debate on the relative merits of the OS. Which one runs Mezzmo with the best performance and fewest issues?