Jorgen,
You know they may all be relatively the same size, two are full frame, two are image stabilized, one has an electronic viewfinder that allows you to see the impact of exposure and white balance adjustments. However only one has all three attributes. Size is only one factor.
As they say "horses for courses", each camera fills a different niche and there is a buyer for each of them
For action photography my choice would be different but for what I shoot I am willing to roll the dice on a A7II.
Jim
You are very right, Jim, and that is exactly my point. What many tend to forget when blinded by the novelty factor is that each camera
has limitations and what those limitations are. The advantages of new technology also seem to be blown somewhat out of proportion now and then.
After shooting with mirrorless cameras professionally and on my spare time for 5 years, I've been running into the limitations of that technology more times than I can count. There are photos of mine that wouldn't have happened without that technology, but there are probably just as many that didn't happen because of it.
In the end, I had to find a camera that would serve me in more or less any situation, and since I do photography in a very wide assortment of situations, there weren't many cameras that made the cut. The crunch is: There are many advantages with mirrorless cameras, but I've lived happily without those advantages for as long as I've been doing photography, and in some areas, DSLRs have been catching up, like video performance and size. On the other side, there are disadvantages with this new technology that it's very hard to live with for certain kinds of photography.
During film days, if somebody had an F5, that was the camera he used and he used it for anything. If he had another camera, it was usually another F5 or an F100. With the latest models from at least one DSLR maker, we are back there again; one body is really all that is needed. Mirrorless isn't there yet. The model that seems to be closest to that is the NX1 from Samsung, but like Sony, they lack lenses and like Sony, I'm not sure if they know the photography business to the core. Sony is probably better at that than Samsung, but they have made some rather counterproductive decisions during the last ten years.
In spite of all technological wizardry that has gone into the 7 cameras, Sony looked more like photography company when they launched the A900. I wonder how many of the Minolta people are still with them...