Hi all,
I just joined APUG and hope to contribute, absorb and participate. This thread got my attention because I too recently got hold of a Mamiya RB67 SD Pro. It came with the 127mm. I've added the 180mm and am waiting for delivery of both the 50mm and 65mm.
As others have stated, all of the lenses Mamiya offered are great, with a nod to the multi-coated (C and later) variations. Ctrout, if you use LightRoom for your 5DM3 images, you might find it helpful to check the focal length you use often, assuming the RB would cover some of similar situations.
My background/story. I purchased new in 1983 an RB67 w/90mm and the 150SF. I only held onto the system for a couple of years as I was also trying to support and feed systems of Hasselblads, Nikons and a Sinar F+ and a 4x5 capable darkroom. Too much, so the Mamiya had to go.
I continued with the three formats until the late 90s when I was about to make a big geo move and the 4x5 system went along with the darkroom. Digital came into my scene in early 2001 and made the switch to Canon in early 2003 and still use Canon professionally to this day.
Around 2012, the lab I've used for 20+ years announced they no longer would be processing film which was a wake up call. Even though I had not exposed a single roll of roll film in over eleven years, I 'knew' I always could. Not so! A propack of Fuji NPH was secured and I took my time running a roll through a Hasselblad. Dust, scratches, long delay in receiving the processed/scanned film finally put me at ease with my move from film.
Ha! 2017 comes along and I got the itch to take a slower more determined approach... and I really missed the larger sensor/film area.
So here I am, ready to deal with what I know film brings to the table. I'll still use my 1-Series Canons and the fast lenses for much of my photography, but look forward to enjoying film again.
Back to the OP lens selection. At the prices these days, it's not like you have to mortgage your house to pick up another lens.
Skai