I think it's better than the Mamiya, but it's all down to personal choice really.
I have a complete ETRSi kit (everything you'll need) that I may be persuaded to part with if you're serious and don't want a 'bargain basement' price. As much as I love it, I've only used it twice since I started using my Hasselblad a few years ago. It's a shame to have it sat in the cupboard doing nothing.
I'm about to go out for the day, so can't answer any questions now, but if you're serious I can post some pics later for you.