Here's a compelling reason to use the APS-C a6000. It has similar file-level output to the first FF generation of the a900/a850 with MUCH less bulk and weight.
Disregarding DOF issues, this is somewhat of an unfair comparison. As of this date, the Sony a850 has available the heavy but excellent Minolta 28-135mm lens and the a6000 has the tiny and modest quality kit 16-50mm (FOV 24-75mm)
...these two are approx. 4.5 lbs. vs. 1 lb.

Of special note, the only other remarkable thing about this image is that it is the absolute very LAST frame out of my now dead Konica Minolta 7D. ... May you RIP:(