i have both, 500C/M (50 and 80mm lenses) and an RB67 ( 50,65,90,180 & 250mm lenses) both have their place in my collection.

the Hassy is light enough to carry around and isnt too big, i mainly use the RB67 for landscapes, do shoot it handheld a lot though, mirror slap isnt a huge issue, with the 50mm, i shot it at 1/15th once with no blur. and 6x7 is nice.