Hello.
The last Panasonic I acquired was a combo from B&H on 2019 black friday, a GX85 with two lenses the 12-32 and 45-150, but I also have a LX100, a GX7 and a venerable G2. Add to this some lenses from Olympus and Panasonic. I also had two Olys E-M10, EMP2, EPL2 and other ones.
What I like from the Olys is the external design and knobs placement, but I sincerely think that the menus asre simply disgusting. They are over complicated without any reason for this. Even the touch interface from Olympus is horrible, sometimes you need to use touch AND keys/dials to set things.
In the other hand, Panasonic menus are clear and intuitive and the touch interface very consistent.
The image quality of both brands are very equivalent, specially if you shoot raw and do the post processing using a decent program, like DxO Photolab.
In the past, when Oly and Pana had only in-lens or in-body stabilization, they were very clore in stabilization performance, but IBIS from Oly had a clear advantage when using old manual focus legacy lenses. Then Oly came with 5 axis IBIS that put Pana well behind it in this aspect. But now Pana's IBIS is equivalent to Oly's.
One thing that Panasonic master is VIDEO. If you make videos, Panasonic 4K is fantastic, specially from GH5.