Quality and brand of a lens makes too much difference. I believe every brand of camera lenses are different schools and not every lens from same brand is at same high level.
Mamiya is extremelly contrasty and good for full depth of field. Someone posted at gallery , Ireland pictures and I suggest to look for them and study his lens. It is excellent and gives the all curves, skin details and shadows plus light plays at the face. Its like classic Hasselblad shots. But this was for bw work. One lens in Mamiya family is really awful may be 110 mm , I am not remembering now and You must be careful before walking on this land mine.
Pentax lenses are too much saturated and gives plastic colors inside shots. But out of depth of field , it gives a noise on the subject like an Leica. If you will shoot from the distance Mamiya is better , if you will shoot crowds from close distance with recording too many out of focus play , Pentax is better.
For color , Mamiya is more neutral if you like pink skin tones. Hasselblad is sharper and better color curve but I found its black is so strong , some of the daylight shadow pictures tend to dark looking.
But overall Hasselblad is winner but I dont like their Distagon