Honestly, there are only really two advantages in technical terms to using stills mode for photography. One is shutter speeds, and the other is data rate.
If you don't care about how much disk space you consume, and you're shooting slow movement, pulling still frames from your footage works great.
Most of the time when I'm doing photography though, I end up with either much higher or much lower shutter speeds than what look in video.
In landscapes especially when shooting f/64 style (which really needs a view camera to do right, even a tilt/shift lens only gets you half way there), typical exposure times are a minimum of 2 second, especially for magic hour, civil twilight, and flowing water shots.
But... I've also pulled frames from clips that would have printed fine. At 24x30 or so, same as what I've done in the past with my A7R... but with the Epic-w the color is better.