FormatOwlSize is only one part of the result
A file that is technically smaller can still be the wrong result if text becomes hard to read, motion turns blocky or pages lose important detail.
The best setting depends on how the result will be shared, viewed or edited later.
Preview before you replace the original
Compare the original and result side by side when the content includes fine text, gradients, faces or fast movement.
Keep the original until you have checked both the visual result and the final file size.