This was not a controlled test but when I first got my IQ180 I took a few shots first with the DF camera and the 75-150 and then with the Rodenstock 70HR/WRS
Marc, I'm surprised at the difference you're seeing. I use the Rodenstock 70mm, and although I've never used the Phase One/Mamiya 75-150mm I regularly use the Phase One/Mamiya 80mm and in truth can't detect much practical difference at all, especially after moderate sharpening.
Phase One commisioned and published MTF charts for their lens range, I understand these tests were conducted by Hasselblad who use the same Zeiss testing equipment and same testing regime that Rodenstock use. In other words Phase One's and Rodenstock's respective published MTF charts should be directly comparable. They suggest that the Rodenstock 70mm Digaron W enjoys a small advantage over the Phase One 80mm and 75-150mm at 75mm, but it really is pretty small.
That ties in with my own experiences using these two lens ranges. Any differences are pretty much swamped by moderate sharpening, with both lens ranges delivering first class quality that, under optimum conditions, are capable of huge enlargements of x15 and even x20 while still holding up to critical scrutiny.
I'm not trying to beat the drum for Phase One/Mamiya, as I said earlier their Hartblei partnership with the 45mm T&S was a mistake, but by and large the practical differences between the two lens ranges are matters for personal preference rather than something that can be characterised as "winners and losers".