I had a deep and wonderful flirtation with all sorts of medium format cameras in the film days but the camera and lens that seemed to yield the most wonderful portraits, albeit with much struggle, was probably the 90mm Summicron on the front of whatever flavor of the year slr camera Leica had on offer to foolish photographers of the time. I'd like to say that this portrait was done with an R6 or an R8 but we had a mix of cameras and since the "sensors" inside were all identical (you got to choose what film you put in..) it hardly matters. But there was (is) something about that ancient 90mm f2.0 lens that was just magic. Or maybe it was the placebo effect. Perhaps we were consistently trying to justify having spent so much more on a lens than we would have spent on one of the Japanese equivalents. The closest two lenses I've used from the "big two" would be Canon's inexpensive 100 mm f2 and Nikon's too expensive (but not in Leica territory...) 105mm f2.0 Defocus Coupling lens.
After having shot several thousand considered images this weekend on GH4's, EM-5's and the stalwart Nikon D7100 I've come to re-understand that the bodies are increasingly meaningless and that the personality of images comes from the lenses with which they were created. Something to consider.