I actually recommend staying 709. Many compression apps will do the appropriate colorspace conversion for you. Additionally there are many issues with proper colorspace handling with various qt codec.
I'll share with you one of my secrets, discovered through tons of trial and error. For best color handling in an h264 file & amazing quality. I use a ProRes HQ source, and run it through the latest version of Handbrake. It's x264 encoder is actually insanely good, and it takes care of the color matrix for you, and does so perfectly. (I should say, I'm doing it on a Mac. Not sure about the pc version)
online editor | colorist | VFX | BD author
http://JuanSalvo.com
