There is a fairly well balanced, up-to-date, 8-page comparison of MILC (mirrorless interchangeable lens cameras) versus DSLRs here:
https://www.digitalcameraworld.com/features/dslr-vs-mirrorless-cameras-how-do-they-compareA couple things they overlook:
1. Mirrorless camera sensors are quite vulnerable in many models. DSLRs have their sensors hidden and "protected" behind a mirror and a shutter when the lens is removed. In addition, their sensor is recessed about 1.75 inch or more inside the camera (to allow room for the mirror and shutter).
MILC, on the other hand, commonly have the sensor only recessed less than 3/4 inch inside the camera and, in most models, it's fully exposed when the lens is removed. This might lead to more issue with dust, fingerprints or even damage (I've already seen a couple relatively new MILC being sold cheap "for parts", because they had a "scratched sensor")
To be fair, self-cleaning sensors help offset concerns about dust issues. And the more forward mounted sensor will be easier to clean.
But I think it's possible that manufacturers will adopt some sort of protective shutter in MILC, that only closes when the lens is removed. I believe that's already been done in a few models, but don't know the details.
I'd also note that it's not actually the sensor that's exposed in either MILC or DSLRs... It's a filter that sits directly in front of the sensor. Another strategy with MILC might be to make this filter more easily replaceable, separate from the rest of the sensor (in most cases now, it's an integral part of the sensor and the entire assembly must be replaced if the filter gets damaged in any way).
2. Price. MILC are "hot". They are the "latest and greatest"... There's rapid growth in sales of MILC and this tends to keep prices high. At the same time, DSLRs are now sort of "old school" and cooling down in peoples' perception... so prices their prices have been coming down. Overall, you can buy a DSLR and lenses for it for significantly less than a comparable MILC. This isn't always the case, though. Some manufactures have kept their prices low, perhaps reflecting the savings in the cost of manufacturing MILC, as opposed to more mechanically complex DSLRs.
3. The above article mentions the limited choice of lenses for MILC. It doesn't mention the lack of other accessories. For example, the article suggests that one way to address the imbalances using a large lens on a compact MILC body would be to add a battery grip to the camera, doubling the number of batteries and adding a bit of heft for better balance. However, grips don't exist for a lot of MILC. The cameras aren't even designed to accommodate one. This is probably because manufacturers think the primary reason people are gravitating to MILC is for their smaller size (which is offset to some extent by the fact that typically lenses for MILC need to be just as large or even larger). This lack of these battery grips also may mean less comfortable vertical/portrait orientation use of the cameras, as many (most?) of those grips also include a secondary set of controls for that purpose.
Of course this also effects the number of shots that can be taken with the cameras between need for battery changes. If a battery/vertical grip were an option for those of us who want and use them, that would help (the limited number of shots possible with "power hungry" MILC is discussed in some detail in the above article). Fujifilm, Panasonic, Olympus and Sony all offer some battery/vertical grips along with some MILC that can be fitted with them... perhaps concentrating on the most pro-oriented, top-of-the-line camera models. Canon's EOS R (full frame) mirrorless was introduced along with and available battery.vertical grip. But their new, more affordable EOS RP model doesn't have option of using one (a "grip" is offered for the RP - in choice of four colors
- but it is merely intended to increase the size of the camera for people who find it uncomfortably small... no batteries, no controls). None of the Canon M-series have option of fitting a grip, either. Nikon has promised a battery grip (no vert. controls) for their two Z-series cameras, but it's still "in development" (
).
4. Somewhat misleading marketing info seems to be a problem with MILC. For example, some of them claim impressively high frame rates. However, read the fine print! In many cases that states the high fps requires "focus locked". Now, I would expect high frame rates to be mostly used for action photography, with moving subjects where focus definitely cannot be locked. It needs to track the subject and update as nearly "real time" as possible. More than one MILC sees their "real" frame rate drop dramatically when used without locked AF. In some cases it's a huge difference.... such as 9 fps possible with focus locked, but only half that rate with it unlocked. Personally, I'd be pissed off if I bought a MILC claiming high fps to use for sports photography, for example, only to find the camera slows to a crawl when I use the necessary AF mode. I don't think I've ever seen this sort of thing with DSLRs.
Rather than vilify someone for asking a common question like "mirrorless vs DSLR", I wish people would either point toward a source of the info they've found most useful or try to add to the discussion with their own observations.
Personally I won't be giving up my DSLRs any time soon. IMO they are the better choice for much of what I shoot and MILC just aren't up to the task yet... the cons outweigh the pros. However, for some other purposes I'm seriously considering a small MILC and a few lenses to use on it. Those aren't high priority uses though, so I'm taking my time and haven't bought one yet.