The first difference, concerning the build quality, is that the A7 has a magnesium alloy body and is weather resistant (dust and moisture), unlike the A6000. You can also see by looking at the images below that the full frame camera is slightly larger, taller and heavier. A7: 126.9 x 94.4 x 54.8mm, 474g. .

sony a7 vs a7ii vs a7iii