What Font File Type for Windows?

Which is Better TTF or OTF?

For designers, both amateur and professional, the main useful difference between OTF and TTF is in the advanced typesetting features. In other words, OTF is indeed the "better" of the two due to the additional features and options, but for the average computer user, those differences don't really matter.

What Type of Fonts does Windows Use?

Segoe UI pronounced "SEEgo" is the Windows system font.

What Font File Type should I Use?

CONCLUSION: Use OTF/TTFall browsers & EOTI.E for Desktop screens and use system fonts for small screens as they render faster. And do consider google fonts. Best choice so far.