Here's a size comparison to the A99ii, which is pretty much an A77/77II body shape

- Nikon-D780-vs-Sony-Alpha-A99-II-size-comparison.jpg (44.62 KiB) Viewed 152313 times

- Nikon-D780-vs-Sony-Alpha-A99-II-top-view-size-comparison.jpg (34.97 KiB) Viewed 152313 times
The Nikon is a bit taller due to the OVF hump, other than that the size is very similar in other dimensions. And a bit lighter. Don't remember people moaning the A99ii was a huge hulk of a camera or too massive to carry around. Yes MILC are smaller, and they have less on body controls too - which brings some compromises.
A few things on the Nikon stick out. I got the new EN-EL15c battery with this, not the EL15B, this has 20% more capacity v the B. Maybe that's because it came out not long ago and they updated their stocks.
Bottom line, using the OVF - this battery just keeps on giving, and giving. You just cannot run it down, even if you went nuts shooting all day. I got on alright with the A99, but you absolutely had to have a spare battery, no question. Plus aggressive power saving on the LCD. I'd no way walk out the door with the A99 with a half charged battery; with the Nikon even if you had 25% no sweat good to go! I can also charge the battery in camera, via USB-C if I need to.
Sony never updated the NP-FM500H. It was stuck at 1600mAh since day one. Yet the cells increased in capacity over the years, even in the same space. That Nikon cell is 2280mAh and a similar size overall. Sony's SLT users would have liked better run times, and Sony could have done that with newer higher capacity cells. They never bothered to, mind blowing really. SLT has much higher power draw, yet they did nothing at all about it.
On this I have dual UHS-II slots, the A99II was stuck with UHS I, despite the good buffer the clearing times are not that fast. It doesn't even hit the UHS-I speed cap, nowhere near it under 60MB/s. The Nikon, yes it's 24mp - plenty for me. You'll get almost 70 shots 14bit raw, and 100 on anything else. Very deep buffer and much quicker to clear the buffer. I don't understand Sony, they have a flagship camera and put UHS-I slots in it. A £3000/€3500 body top end price for many. There are certainly things I don't like about the Nikon - which I will go into more later on. They seemed to get the obvious things mostly right though