Here is one review/ comparison I found. I do not know if this is from any brand-supported reviewers, so I cant vouch for any paid bias or not.

From Photography Life: Best Camera for Sports and Wildlife Photography in 2023
https://photographylife.com/best-camera-wildlife-photography

The OM System is excellent for wildlife shooting and I know many who love it. We wont get into a debate into the image quality pros and cons of micro 4/3rds vs APS-C vs Fullframe. Use the format that suits your image quality needs and be happy.

Full disclosure, I have used APS-C and fullframe for my wildlife shooting in the past, and I prefer fullframe image quality with high megapixel cameras like my 50mp Sony A1, and 61mp A7RIV, and fullframe E-mount lenses from Sony, Sigma, Tamron that can resolve those high megapixel sensors.

However you would not go wrong to go to the superb OM System. You can make excellent photos with it, and save size and weight. Not sure how much money you will save in the long run with the best OM lenses, but that needs you to do further research .

If after doing your research you find the OM system is best for you, go for it and be happy.

Cheers and best to you all.

I changed to Olympus m4/3 system in early 2017 after a shoulder injury that made my FF Canon gear too hard to handle. I really like the size and the selection of Olympus gear. I have shot this kit in Tanzania, British Columbia, several times in Alaska and in the state of Washington, photographing wildlife, both birds and animals.

My experience is that in low light at ISO 6400 shooting eagles and also bears, the images are a bit noisy. When I am smart enough to keep 'exposure to the right' then the noise cleans up pretty good in LR. Most of these images are with the Panasonic/Leica 100-400 lens, not the Oly 150-400.

I suspect that the really high megapixel FF gear from Nikon, Canon and Sony will produce images a bit sharper at the same ISO levels, but for many of us amature photograpers, the quality is very good with Olympus kits.

I just wrote a note to Jan Wagner with a request for him to field test a 4/3 OM System/Olympus OM1 camera and a couple of its wildlife photography/scenic lenses. With a fast check in YouTube, there are several photographers switching to the OM system. There is no way to tell the connection those photographers have with Olympus. I think Jan Wagner could provide an objective review. Further, I would be interested in knowing from UHH pro-level members what they have discovered in the serious field testing the 4/3 OM System. Realistically for many of the UHHers, the $$$$ of the higher level full frame RF Canon lenses and Sony bodies are not within our price range.

If you believe the 150-400 is heavy and expensive, you should try to imagine what a full frame equivalent would cost and weigh.

That would be a 300-800 f/4.5 zoom with a built in TC that would get you 1000mm. It hurts my shoulders just thinking about it, and you'd be cryung all the way to the bank.

And you probably wouldn't get nearly as good weather sealing or IS.