I've worked withing pretty much EVERY major and obscure operating system out there from
DEC PDP-11's OS to VAX VMS to OS-400 to Z-os to MS-DOS 1.0 to 7.0 to Minux, Xenix,
BEOS, Theos, QNX, MAC-OS from 1984 and the Apple Lisa to Windows from earliest days
to Linux (10 different distros!) tor our Internal Midgrid-OS!
Of all of them, the best commercial end user-friendly OS is Windows 10 -- Mac OS annoys me when I can't right click on an icon to get it's properties or perform a pre-defined action!
The best Server OS I think is actually Windows 2000 Server because you could STILL install it in
ANY directory you wanted and it STILL had the most admin control while still having all the best features of Active Directory which is the BEST client management system ever! Windows Server 2016 has too many admin restrictions on it!
For embedded devices, QNX is the Numero Uno OS software as it TRULY is a fail-safe OS!
They use it in Nuclear Power Plants and other Critical Systems so I'm all in for using it on my
custom video and audio playback/recording box. Never failed in almost 8 years running 24/7/365!