@CFynn,
> You said ” No mirror slap and the leaf shutter will have less vibration than a DSLR’s focal plane shutter.” <
Never head that MODERN DSLRs has this issue. BUT top of lines mirror-less camera had “Shutter shock” issue, try to search “Olympus shutter shock” for example.
> You said “There is also some loss of IQ in a lens with OIS. <
“you can turn OIS off” as Tonio Loewald said.
Also, High-end P&S can turn off OIS automatically if there is no movement being detected, the LX7 will turn off OIS automatically when tripod is used for example.
BTW: Tamron just release an ultra-wide angle 15-30mm F2.8 lens with OIS for FF.
Bottom line:
– It needs experience to make high performance OIS, and
– OIS Lens is much more expensive than whiteout.
– For sharpest results, you may need couple more stop than 1/FL.
– You need IS to shot video as you may hold the camera steady but you are moving the camera or even walking…

Started out doing photography at the age of 6 using an uncle's old 1940 kodak brownie box camera. At 15 years of age, I decided to buy my very own 1975 Praktica SLR camera. I now shoot with a Nikon D850. I do unpaid TFP and commercial paid work.