What I can say about KDE Plasma 5 that I can’t say about Windows 8
linuxbsdos.com
linuxbsdos.com
In my experience KDE 1.0 was the "best KDE desktop ever." At the time, Microsoft was offering Win 95 (a toy compared to Linux) and Microsoft NT 4 (unstable and FUBAR despite everything microsofties say)
Windows has gotten much much better since then, and Linux has improved on the server (after years of suffering, Linux finally got stable on multiprocessor machines.)
The Linux desktop has been stuck in reverse for the last 20 years, however. GNOME and KDE come out with releases that periodically rearrange the deck chairs, but don't offer any value to end users.