1 is the reason I'll never use Win10. I don't trust Linux, even in a VM. Too many people have access and I am forced to assume it's insecure by default. My assumption will never change.
2 is inconsequential. I can use a "dark theme" in Win7; all I did was disable Aero and set up my desktop the same way I had since Win95.
3 Firefox
4 Okay, good reason.
5 The Win10 (actually, WinVista+) start menu is pointless.
You trust a closed source OS from a developer already proven to be willing to engineer backdoors and lie about it over an open-source OS? Can you explain your reasoning?
I don't actually _trust_ either one, but I would certainly rank Windows below Linux.
Also note that the linux runtime in Win10 is not installed or activated by default; you need to put the OS in developer mode and install it yourself. If an attacker can do that externally, he already owns your system.
1) Linux on windows runtime beta (commonly called bash shell, but it's much more)
2) dark theme
3) extensions in the Edge browser
4) Vastly improved stylus support
5) Slightly changed start menu
6) Improved action center, if you use UWP apps