It is not a huge loss though, because pros almost exclusively buy their DSLRs from Canon and Nikon.

I have to disagree about viewfinders and batteries being inferior. The viewfinder is an acquired taste. If you look at cinematography and movie production, you’d need to search for a long time before you found an optical viewfinder. And I just shot a 12hr production on a single battery, using the highest resolution DSLR on the market. No pro photographer will ever need more than a day of battery life.

I respectfully disagree with that. Current generation viewfinders have excellent resolution and very little lag, and while that will never be as perfect as an optical viewfinder, they do have the great benefit of being able to show you the image as it would be after exposure (so you can see which parts would be over or underexposed for example), and can overlay much more useful information.

Don't forget that EVF can surpass OVF in image quality because they can apply lens correction to the viewed image which brings the image closer to the final product. (although AFAIK it's not done currently)

Canon and Nikon are also shifting en masse to mirrorless. So the tides have clearly changes across the board.

I upgraded last year to a Sony A7ii, and this one's even better.

The tl;dr is that, at this point, optical viewfinders are overrated. The best EVFs are just as good.

Pros aren't married to glass or to viewfinders, though. They're married to lens mounts. Glass investment dwarfs camera body cost. That's the sticking point.

The worst part of the A72 was the battery and the buffer. The A73 made both of those concerns a non-issue.

It's not so much that "mirrorless tech. has basically whooped moving-mirror tech. 's behind in a major way." But that mirrorless tech has gotten good enough that the inherent advantages of eliminating the mirror aren't overshadowed by the need to use an electronic viewfinder instead.

Huh? EVF and OVF have their own advantages but it is not correct to say optical quality of one is better than the other.

EVF can do things such as boost the exposure which makes things like the 800mm f/11 possible. This would be much too dark otherwise on an OVF.

EVF can also electronically correct the image for certain types of abberations that the lens introduce.

EVFs also don't introduce their own abberations that OVFs do because there isn't as much glass or mirrors to move the image from the lens to the viewer.

OVF certainly have advantage from being a "live" image for tracking purposes but EVFs have mostly caught up enough to make that difference negligible.

But modern EVF is good for most purposes. And I'm sure the newest Canon digital bodies have even better ones than my Fujifilm X-E3. (Which itself is at least "good enough," while the X-E1 was more like "mostly sufficient.")

But these particular SLRs? Nah. They were nice and all, but not particularly differentiated in any way.

Whereas an EVF can fairly accurately show you composition, exposure at current settings, any sort of raster graphic they want on the screen (eg the head silhouette to frame passport shots), etc.

My biggest gripe with the EVF is that it kinda sucks for astrophotography. I have to crank the ISO way up, take a test shot, and then turn it down before a long exposure. Our eyes are just much better at focusing on dim points in the sky.

They are very different. Even though that DSLR is eight years old, it gets battery life that any mirrorless camera can only dream of (>1000 shots without a battery grip). Even though the mirrorless has one of the better EVFs among it's peers, the resolution is not quite as good as the OVF, and it does have visible lag and smear that the OVF simply doesn't have (the EVF is a 85 Hz OLED with 1280x1024 pixels or something like that, iirc).

The DSLR has a faster AF if you are wildly out of focus, though the AF is overall much worse - the mirrorless has like 10x as many AF points, and they are all over the frame, and it has flawless video autofocus, as well as almost perfectly accurate autofocus.

The full-frame mirrorless is about the same size and weight as the APS-C DSLR. A full-frame DSLR would be quite a bit bigger and heavier.

The real difference is that you get a lot of stuff just like that in a mirrorless which are somewhat of a pain in a DSLR. Viewfinder magnification, good video AF, silent shooting with the viewfinder, customizable finder display, nightvision, histograms, distortion correction in the finder (critical for precise framing with ultra-wide lenses), focus peaking etc.

There are some differences which are pretty much purely hype. Things like eye AF for example pretty much only matter for people who mostly do "ultra-blurry background" portraits which have such a thin depth of field that when the iris of the eye is in focus, the eyelashes are already blurry. It's a very specific thing to do, but gets around 90 % of the air-time in "totally independent reviews I swear I'm not sponsored".

At the current top-end, DSLRs like the Nikon D6 are said (not that I would have any idea about that) to still have somewhat faster AF than comparably expensive mirrorless cameras.

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As for Sony, they inherited the A-mount when they bought Konica-Minolta. The A-mount was at that point in time already a legacy mostly-mechanical-with-some-electrical-bits-kind of mount (e.g. mechanical aperture control, mechanical autofocus through a coupling in the mount). The E-mount is a modern, fully electronic mount, though designed for APS-C (full-frame just barely fits into it). I think when the E-mount was introduced it should have been clear that anything A-mount is on the way out. Also, A-mount SLRs where never particularly high-end, so in terms of performance I'd expect them to be significantly below what Nikon and Canon offer, especially because it does not seem like there was much development on these after the E-mount was introduced.

Just like Nikon F is clearly on the way out with Nikon Z being around, an Canon EF being on the way out with Canon RF around, the same is true for the A-mount.

I swear that my 2008 Nikon D700 had functionally unlimited battery life. My mirrorless camera would be hard-pressed to get through a day of shooting on vacation on one battery, but that tank seemingly had a Mr. Fusion inside of it.

(And the battery life is the real killer.)