First of all IQ is only marginally better than the ELP-10 and it will remain that way until Sony or others figures out how to make a 32-40MP M43 sensor work. If you are looking for significantly better IQ you can buy a Sony A7C which has much better IQ and auto focus accuracy. The A7C with the 28-60 zoom cost less than the OM-1, has a smaller Nauticam housing and can shoot from 130 degrees to 1:1 with the WWL-1B and CMC-1.
My point is not that I think the A7C is a better camera than the OM-1 but that I don't think most folks are buying the OM for IQ as much as for the other excellent improvements over EM-1 II/III.
Let me list a few.
#1 without OM Systems Olympus would be dead and not only have they kept the brand alive they have raised then bar with two new excellent new lenses, a top of the line new OM-1 body, an IP-53 rating for weather sealing which is best in the industry and more.
OK and?
#2 A much better battery 520 v. 420 base.
Never had an issue unless you use the supplied flash in ttl to get to a whole day of diving
#3 better focusing system made possible by the stacked sensor which speeds-up everything allowing 1053 focus points rather than 121.
There are now consistent reports of AF problems in single point mode
#4 I can't stress this enough, EVF of 5260 v. 2360 and LCD of 1620 v. 1037. these specs are higher than many over $4000.00 "pro" cameras.
Majority of underwater mirrorless users do not dive with a viewfinder but use the much lower resolution monitor
Remember that the actual resolution has to be divided by 3 so the current EVF is 1600x1200 pixels while the old one was 1024x768. Panasonic has had 1280x960 since few years and that is adequate
#5 I am not a video guy but I know that 4K at 60P in 10 bit makes this camera qualify as a hybrid stills/video choice. The EM-1 III 4K/30P is a bit antiquated at this point.
Video is average with this camera and the exposure tools are poor.
I wish that OM Systems would have added a base ISO of 100 or even ISO 50 with expansion. Going to ISO 102400 on an M43 sensor is not going to beat full frame but having a lower base ISO would add real value to the system.
That is not possible as they try to minimise noise they need to increase base gain. This camera is optimised for shadows and has less dynamic range than previous models marginally of course
I am not suggesting that every II or III owner needs to run out and switch systems but my original premise stands that OM-1 is the best M43 camera made for land or sea.
Depends on what is your use case. Generally Olympus camera are favourite by bird shooters or small critters hunters. For all other use cases they do not offer any real advantage as they run short of DR and have issues of fixed pattern noise. I have used one so I know...