I suspect that this has been discussed elsewhere, and if so, I would be grateful for links. I use a Mamiya 7, but am wondering whether a higher megapixel slr (24mp) is likely to give the same level of sharpness and depth. Notably even small photographs taken on medium format have a kind of sharpness and depth that is not replicated taken either on 35mm or DSLR 12MP, and I wonder if this is replicated with higher megapixel slr cameras. Thanks for your help.

I think you'd be best off renting a 1Ds Mk3 and maybe a medium format digital back, take some pictures of what you're usually shooting and do a comparison yourself. It's really the only way to know if it meets your own standards. Personally I used to shoot 6x7 before going digital with a P25 and I'd never dream of going back to film, but that's just me.