>So difference between 1Ds III for example having x0.76 magnification means that it is quite bigger than D3 or D700?<
No, not quite a bit - just a little bit bigger. You can get a DK-17M eyepiece that gives you 1.2X magnification for 35.00 that makes the Nikon's quite bigger than that. I'm pretty sure that you could get a similar eyepiece for the Canon. Plus it isn't really relevant comparing a 1ds MKIII to a D700 - and the 5D is "quite" obsolete and due for an upgrade very soon.