I believe on demand to be best. I have been switching between no profiles and having a screen off profile recently.
Mainly because I have ubuntu running from my android device and vnc-ing from my pc, so don't want performance to take an impact when screen is off. Oddly I switch to performance governor when running ubuntu but even with no screen off profile, if I'm running an apt-get, it seems to hang for a bit until I put the screen on.
Definitely still believe I'm getting better battery with having the screen off profile by the way....
128-245...
I know what everyone says about screen off profiles not being needed and not bringing anything to the table but I genuinely notice a difference