The best way to show the problem, is via image.
So, here's my image: OneDrive version of pic
After you click the link, you may need to click the pic again to "zoom in" to the correct full picture size. THEN, I'd encourage you to use the "Magnifier" Windows Accessory, to zoom in to 400%, to inspect the results.
As you can see, I typed "Personalize", using Segoe UI, at different font sizes. And I typed the letter "L", in lowercase, several times, at different font sizes.
You can clearly see that Word 2013 acts a certain way (greyscale sub-pixel antialiasing, used by Modern UI applications, Office 2013, Internet Explorer, and more and more parts of the Windows 10 OS), while Notepad acts a certain way (RGB color sub-pixel antialiasing).
I'm saying that the greyscale version looks very very MUDDY, and INCONSISTENT. Look at those lowercase l letters! Each one is slightly different! And when not zooming in with Magnifier, the letters look like they're muddy and falling apart!
The RGB color sub-pixel antialiasing, while sometimes giving a tinge of too much green or a tinge of too much purple, is at LEAST consistent and crisp, on my LCD display. A lot of us are used to it.
I hope we can, at some point, give the user the option. I'd choose the RGB any day of the week. I've had to avoid using Modern UI apps, because of this very issue.
Regards,
Jacob Klein