Okay Friends I said somethings as i answered.
I am a gamer I ran some bench i always got a massive amount fps more on XP .
None of PCs are looser , they are terribly fast . My XP boots up in 5to7sec with SSD. Esed is my AV .
I haven't formatted my pc for two years . ALl My trim utility and Avg Tune up utilities kept it alive for long time .
I have following oses in my 500GB Toshiba SSD
Windows 2000 Professional (sp4+tomasz86 update pack + Kernelex by BWC)
Windows XP Professional Sp3 32bit
Windows XP Professional sp2x64
Windows Server 2003 Data center edition Sp2
Windows vista ultimate x64 sp2 + Platform update
Windows 7 professional 32bit sp1
Windows 8.1 Enterprise x64
Windows 10 Professionalx64
In this circumstantial , Server2003 is fastest , XP is after (Heavly tweaked) and then 2k comes to win the battle. SO no query NT5.x is leader.