I can "sort" of see where Snerkler is coming from (although I have no intents on changing any of my gear).
I love my Nikon Z6 and Z7 bodies almost as much as my Olympus, and obviously under
certain conditions the FF sensor just outshines the Olympus and the images from both the Z's are stunning, with the shallow DOF and "pop" that Snerkler mentions. I think Nikon is on a roll with the Z bodies with the fast roll out's of the new firmwares, and I honestly don't think it will be that long (and maybe a camera generation) before the Nikon bodies (and Canon for that matter), achieve the AF capabilities of the Sony's (I really believe in the 18 months since the Z's were launched, the AF in these bodies has come on leaps and bounds). The AF on Sony's is generally regarded as pretty much the best in the business at present, but I don't shoot a lot of fast moving stuff and for the little I do, neither my Olympus EM1 MK II or EM1X or my Z6/ Z7 combo have ever failed me in that regard anyway. Really fast small birds in flight might be a different proposition though. Ergonomic wise (for me at least) all 4 of my bodies are just superb in that matter, and really makes you want to pick them up and shoot. TBH, even with the Z7, I don't use the full 45mp most of the time and quite often crop or resize down, so don't know what I would do with over 60mp
However.....the one thing that Sony has that Nikon (and Canon for that matter) doesn't is a full suite of legacy mirrorless lenses. I have to admit to longingly salivating over the Sony 200-600 OSS lens, at less than £2k (in fact grey - less than £1.4k). Now I know a Nikon 200-600 and a 100-400 is on the road map, but it's not here YET, (and maybe not until next year), and at Nikon prices, I expect it would cost a lot more than the Sony.
That's for me where my Olympus system comes in. I currently have 600mm effective at F4 (so if you take it that FF has about 2 stops better high ISO than M4/3), so I'm only 2/3 stop difference (all else being equal - F4 vs F6.3), so that will do me for now, and with my new NR routine (using Denoise AI), I'm pretty pleased with images from the Olympus (certainly up to ISO 3200-4000, and with a bit more care - ISO 6400). To be honest I've thought a few times about going all in with my Nikon FF gear and selling off the Olympus but whenever I do, I remember the things about Olympus that I love i.e. Smaller lenses in general, HIgh Res mpdes (hand held and tripod), Live Time / Bulb / Composite modes (love these), world class IBIS that hasn't been bettered, a sensor that just doesn't seem to get dirty, built in focus stacking (that actually stacks in camera) and many more. What Micro Four thirds might lack in sensor size, it more than makes up for in genuines useful features that most of the competition just don't have.