Last year I bought a full frame camera again, wishing to have a quality modern 50mm/1.8 autofocus lens, and I also have an ancient screw-mount 50mm/2 that I like to use with it.
Even when I bought it (and it’s better than I had any right to hope), I did not consider it to be my main camera. I’m fortunate that I’m at a point in my career that I can buy into a second camera system, but even if money were no issue at all, micro four thirds would remain my main one.
It really comes down to your individual interests and what you want out of a camera, and as many here have said, freelance peer-pressure marketers don’t do the same things with a camera that we do.
So, what’s the advantage of a smaller sensor if the camera isn’t any smaller?
How about speed? Both Olympus/OMD and Panasonic have frame rates in raw with continuous autofocus around triple what a Nikon Z9 can do. If your subject allows locking the focus (like waiting for a bird to take flight, or land on a perch you’ve already focused on), an OM-1 will out-do a Z9 by a factor of six. It’s rare that someone needs that kind of frame rate, but if you need it, you need it. It’s how I got photos like the ones here: Go around! Landing pad not clear! and those were with a camera I got for less than $800 and a lens I got for around $500 (and only 50fps).
I don’t prefer comparing ISO number, because I think it obscures an important point. If you aim for the same Depth of Field, you take the same amount of light, focus it into a quarter of the area, and quadruple the brightness. Half the focal length, two stops faster focal ratio, two stops lower ISO to get the same photo. At that point you have the same choice anyone else has: smaller lens or less noise. I own the full frame camera because I love fast standard primes. It’s all individual desires.
But, for example, I will never buy a macro lens for the full frame, and I love macro. If I’m stopping down to f/6.3 for usable DOF anyway, what advantage is there using full frame if now I have to go to f/13?
On the subject of high frame rates and macro, what matter if I can’t focus on honey bees in flight if I can simply let them fly through my plane of focus with the shutter button held down? Every nice micro four thirds camera lets you buffer photos without writing them to a card, and as soon as you see the shot you wanted, you press the shutter release the rest of the way down and the camera writes the last half second or so to the card. When focus peaking flashes the outline of the bee in my viewfinder, I’ve got her!
Huh, this came out quite long-winded…
I recently was able to buy both of my dream cameras, a mid-range full frame last year, and a flagship (but no more expensive) micro four thirds camera last week, and I could not be happier. The new camera isn’t even any smaller than the full frame, but with some of the sharp tiny lenses I own, it still travels with me to work when the other stays at home.
Edit to clarify: career is not photography related