I am on record repeatedly as saying the little, budget 75-300 Olympus lens punches well above it’s weight.
Recently, testing for something else, I had a chance to compare it to the 12-100 at the same focal length.
The goos news for me is the perceived sharpness compared to the excellent 12-100 is good (these are 900x700 crops). What stuck me most though was the difference in contrast. The #5 looks to be basically the same in both images, but look at the tarnish marks on the panel. They look like they were shot in different light, but they were not.
The cheap zoom is sharp and pleasant looking and is possibly more contrasty in a basic, more global sense, but you literally do not know what you are missing.
The dearer lens is sharp and very micro-contrasty, rendering the leatherette panel better and revealing the surface tarnish.
Neither is better generally speaking (the reduced micro-contrast lens has it’s uses), but I feel they are well designed to purpose. The 12-100 is for professional landscape and general shooting, the 75-300 is aiming at keeping the serious amateur content.
I checked several images, fiddled with settings and processing, but the difference stayed the difference.
The 12-40 seems to land somewhere in the middle.
It looks like the design of the 12-100 is similar to the excellent 12-60 for the 43 cameras (very high micro contrast and very fine detail).
The 12-40 was designed, as Olympus have stated, to be a little less focussed on fine detail rendering, aiming for a gentler, more pleasant look, probably in response to the sharper sensors they are offering.
The 75-300 is aiming at the more achievable and probably more relevant to a cheap tele, high contrast, but not high micro contrast rendering.