I got the battery conversion for my 500ELM, which BTW, cost about half what my old 500C cost. Don't know why, they seem very reliable if a bit noisy, but what Hassy is quiet? Agree that they are very nice to hold, but the extra weight may put some off.
One advantage is that you have a sort of Moon camera, and they sound like a SX70 when they fire!
A hasselblad is far from subtle anyways, I'd go for an ELM
I used to use one in the late 70s when working as a wedding photographer. I preferred the feel and handling of a 500C. The ELM fealt ungainly and unbalanced to me.