Megapixels for video: A7r advantage?
For video using autofocus with native lenses, the A7 has a clear edge. However, if one plans to use the body for video with manual focus legacy lenses, could the A7r's increased resolution provide any advantage?
In the case of the A7r (and many non-dedicated video sensors) more megapixels is worse becuase of the way data is read off the sensor. Often it skips lines and or columns in the array. This leads to moire and just isnt a very good use of the sensor (youre not using all of it).
The newer generation of sensors are able to read out the entire sensor for video (e.g. the one in the RX10)... but, this isnt true of A7 or A7r.