Hi,
I remember that the "on-line photographer" did an article about that but with M lenses, not R.
Do not saved the link but it's there, make a search in his site.
The interesting point is that he noticed that there was not an increment in term of IQ with Leica M compared to the mf lenses,
So, by extention, logically there should not be either an IQ increment using the R series, but sometimes logic is not where you expect.
The "logical" reason why there was not a better IQ with top class expensive lenses in because that mfd small sensor is not capable of delivering
the full potential of these lenses. They sort of reached a top where if you want better you need bigger.
They did brillantly, but there are stucked now into a format that soon will be overpassed by new EVILs cameras players with bigger and more powerfull sensors.
I put a thread here called "MFT is a dead end format", and it was not well received by many of their users, fair enough when you have invested in a gear.
But I've been a FT owner and saw what happened to that because of the limitations of the smaller format. Now, it's fair to say that MFT is a mature system and very well acheived.
By the way, I've been claiming for years, sign the petition etc... for a digital R9 successor instead of the extravagant (but excellent) S2...that would have been just the right thing to do for Leica IMHO. That, no doubt I would have purchased one. But what's done is done.
Regards.