I started with Minolta, so i'm now shooting a Sony A55. I like it, but it kept freezing up in Death Valley. (Solved by taking the battery out and waiting a while -- missing the light.)
It has a "cropped" sensor [APS-C]: the image recorded is smaller than if it was 35 mm film. This has curious effects when it comes to lenses. A 400mm lens' enlargement on a 35 mm "full frame" sensor has a different angle of view than on a cropped sensor.
Apparently my choices in the Sony line are the cropped sensor A77II (~$1k) and the fullframe A99 (~$2k). That seems obvious, but the A77II doesn't have a GPS: this is a significant issue for me. I use the GPS in my current camera for part of my recording of plant locations.
So, should i even stay with Sony? In looking at comparisons of the two cameras, i came across commentary about how Sony is going to direct development away from the "DSLR type body" [https://www.wimarys.com/sony-a77ii-vs-a6000/]
I go off and look at medium format cameras that make the A99 look inexpensive.
I've managed to stay out of Cannon vs Nikon for so long, i've no idea how to judge between the two.
"The Sony LAEA4 Adapter enables A-mount lenses to be used with E-mount cameras ...Key features include: Full-Frame Compatible."
Ah-ha, Sony will still have full frame sensors, just moving to the E-mount lenses. The adapter is $348.00.
Sony A7 II ... oh, these don't have GPS either.
I'm going to go have a sulk.