digital back on MF vs digital 35mm?

Howdy!

I'm hoping this isn't a too obvious question.

I watched a professional shoot the other day and the photographer had a
hassey with a H1 digital back.Which got me wondering - what is the advantage
of a digital back on a MF camera compared to a digital SLR, assuming the
lenses are comparable (ie. zeiss vs zeiss)?

With film, the format size is a significant factor between MF and 35mm. With
digital, is it a question of electronics? If the electronics (sensors,
chips, etc.) AND the lenses are comparable, is there any advantage of MF
(w/digital back) over a digital SLR (35mm)?

While I've been shooting film (35mm & lately MF) for over 20 years, I have
been studying the digital scene for the last couple of years. I've decided
it's only a question of when before I make the leap into digital as well.

Thanks for all replies!

Norm