Anyway, the high-end dslr like the canon 1Ds MK3 or Nikon equivalent are absolutely capable for the most demanding profesional tasks, specialy the last models.
I just come back to a meetic with an important fashion photographer and we talked a little bit of gears for a while, he just uses now exclusively the Canon and does not shoot any more MFD, even for big campaigns. No problems, the Canon just does the job fine.
I could see some big prints in the studio and they are perfectly fine for any serious exhibition.
It is just a question of choice where IQ is not the only factor to consider, but many aspects.
Again, for what I learn from the big pros, and it is curious that we do give it so much importance in the forums, is that IQ, DR etc...are the last things they are talking about when it comes to a choice of gear. Simply IMO because any kind of modern pro camera 35mm o MF has enough IQ and DR.
But more often if not always, what matters for them is if there is a safety conection, handling, data transfer, range of lenses and accesories, reliability etc...
I've never heard a serious Pro that I've worked with preocupated by the IQ or DR of his gear, I'm not kiding, never. They might be some of course, but in my experience I do not know one. Always periferical technical aspects like the conections (this, very often) etc...
So I think that it is really important that one base his choice on other aspects than IQ and it is obligatory to try a camera before. If your camera has 2000MP and 200 stops DR and even makes you the cofee, but you feel totally unconfortable with its handling, you will never be satisfied with it, regardeless its specs.
Regards,
Fred.