FWIW, Both Cookes and Leica's are similar in the fact they are lower contrast lenses in comparison to something like Ultra Primes. From tests of my own and from what I have seen from other people's tests, the MiniS4's actually are just the tiniest, smallest bit less contrasty than S4's, and Leica's seem to be less contrasty than S4's too. Remember, we are talking about really small observations here.
Both Cooke and Leicas have been described as "smooth" for this reason. They are plenty sharp, but sharpness can be skewed by the contrast. Higher contrast can give the illusion of being sharper. Both Leica and Cooke are sharp but smooth.
It's more than that. Cooke's are designed to flare in the coating layer which corresponds to skin tones. The other layers, do not. Thus they help to retain sharpness, while the warmer layer actually smooths the skin out. That's the secret sauce that is behind their coating technology for many years. Sharp, but soft where it counts.