After going through my RB67 vs. Hasselblad test. I decided that the I could not tell the difference in image quality. Both cameras produce remarkable shots but the viewfinder on my RB is so much brighter and easy for me to use, I sold the Hasselblad. I did like the prism finder in the Hasselblad kit and of course the weight was wonderful. But the RB has 6x7 format which suits my style better, the rotating back, easier to do double exposures and something really simple, a place for the dark slide to go.... That may seem trivial but I liked it.
I have had the RB for a while now and want to expand mt lens collection. I currently have a 127mm Sekor C and a 90mm Sekor C. When I first got the camera I got the 127 because is was available. Later I got the 90 and I think I like the framing with the 90mm better???
So after all that what would be recommendations for a second lens 65 or a 50mm? I will tell you that I find I like my 28mm f/2.8 in 35mm format a lot.