It all comes down to this. Control. Control the environment, control the lighting...and most importantly, control the camera. The HV20 is a phenomenal camera and I'm surprised we haven't seen more from indie filmmakers yet doing their feature films this way (I just shot one over the summer - in post right now).
Cinemamode has benefits, but none of the benefits trump locking down exposure and aperture. Cinemamode takes control of things you won't notice until post production and then you could be faced with a reshoot decision. TV48, manual focus, lock exposure and light the scene properly. That's my 2.