Put three prints of the same subject, same body (say a Canon w/adapters), same shooting aperture, etc with no PP other than some USM (e.g. no trying to equalize colors, contrast) and I suspect most viewers would pick the ZF or Leica prints over the Canon's:
Better micro and macro contrast, more accurate color (no Canon over-the-top reds and yellowish greens) and with the Zeiss, more of a 3D 'pop' effect.
Sharpness-wise it would be fair to call them on-par (or close enough not to matter), the greater differentiators will be how the shooter prefers their macro/micro contrast, color, temp, skin tones, CA, etc.
Another lens to consider is the Leica 35 Summicron. Easily adapts to an EOS body (summilux not so much unless you shoot APS-C) and a hell of an optic. ZF beats it WO, but after that....
Better micro and macro contrast, more accurate color (no Canon over-the-top reds and yellowish greens) and with the Zeiss, more of a 3D 'pop' effect.
Sharpness-wise it would be fair to call them on-par (or close enough not to matter), the greater differentiators will be how the shooter prefers their macro/micro contrast, color, temp, skin tones, CA, etc.
Another lens to consider is the Leica 35 Summicron. Easily adapts to an EOS body (summilux not so much unless you shoot APS-C) and a hell of an optic. ZF beats it WO, but after that....