I don't use these camera side by side, but when I shot a Phase p 30 (I think) and the 1Ds3 in a controlled test with strobes in the studio last fall, I did not see any appreciable difference in DR. This was shooting RAW and trying various converters. Even hunting around in shadows and using + exposure looking at the "shadow detail", there was very little difference in detail. The Canon did show more noise when boosting the shadows 2 or more stops looking for differences. Though I have never shot in image in real life where I have had to boost shadows by two or more stops.
The highlights seemed to clip right around the same point too, showing not much difference in DR.
Other than that, I have not shot MF and current 35 systems side by side in any controlled manner...
I have shot most 35mm cameras next to medium format in a lot of real world productions and I don't think anything I see on the dxo site is that far from my own viewing.
As Michael says trust your eyes, but I think you can take this one step further (at least if you work in commerce or editorial for clients) and say trust your client's eyes, or even trust the viewers eyes, because if anyone sees any difference between the current line of high end dslrs to medium format will be seen more in the ability to capture the moment or get an image in focus than any pixel peeping comparision or lab tests.
In the end it really doesn't matter to the viewer what it was shot on if the image is compelling and it doesn't have an obvious flaw like missed focus or wildly out of range exposure.
Recently I shot a campaign where a woman is running out of a subway platform with heavy cross side light. I shot it with the Phase p30+ and a Canon 1dsIII and except for the different look in lens and AA filter I really could not see any appreciable difference in highlight to shadow.
In fact I shot some of this session with a Nikon D90 just because the focus sensor array covered more of the frame and when we put those d90 images in the computer on locaiton, I thought the d90 would really be awful compared to those other cameras. To a person, we were shocked at what a small difference there was expecally from the d90 to the Canon. Just nothing that noticeable and since more of the d90 images were in focus that ended up as the select.
Were talking about $900 cameras vs. $7,000 and $22,000 cameras and once again in the real world nobody noticed that much of a difference.
I'm not advocating everyone throw away their p45's or Leaf aptus and go buy a box ful of $900 cameras, but once again, in the real world this proved to me that medium grade consumer cameras have come a very long way and in fact have come much further than in a shorter amount of time than the high end specialty cameras.
In fact if a Leaf, Phase of Hasselblad had the lcd screen, shutter response, higher iso capability and focusing of a D90 it would be cause for massive celebration.
I work with one in house pre press manager that I think is probably the best pre press person in the world. He has written his own cmyk conversion and moved this retailer to a complete digital workflow and his group processes over half a million images a year that run on building sized posters in times square all the way down to instore, catalog, print advertising and the web and he will be the very first to tell you that anything over 20mpx is just not that noticeable once it gets through retouching and into print. In fact he would rather see a weeks shoot come to him from a dslr than from an medium format back because he sees less pattern moire usually more in focus images and finds the whole process of seeing a decent embedded preview for edititng to be a real benefit.
Then again if I was staring down half a million images a year, I would probably feel the same.
DXO labs or not what all of us know is for medium format to prosper they are going to have to up their game and offer more than just more megpixels. They really need to have a rethink on the whole process of how their cameras work in the real world and they are going to have to be positive that what they offer is more than 20% better image quality (whatever that means).
Still, and to be clear, I'm actually not advocating anything other than a compelling subject, beautiful lighting, a unique viewpoint is much more important than any chart comparing DR down to .003 of a difference or 5% more eyelash detail. Don't just trust your eyes on what you see at 200% on a computer screen but also trust your mind in knowing that the camera you used allowed you to shoot what you wanted.
I'm setting on an invesment of tens of thousands of dollars in digital backs and cameras and though they still have a use, I have to keep in mind that just because I bought them doesn't mean I have to always use them.
I actually find all of this amazing that so many photographers will go into a catatonic state if anyone dare say a Canon or Nikon performs better than a more expensive system, but instead of sticking there noses on a computer and comparing each pixel, I suggest step back and look at the image and in fact look at it the way you want your viewer to sees it.
In fact I would think that these are times to rejoice rather than condemn. I'm personally happy that lower costs cameras perform so well, but then again I care a lot more about the photograph that I do camera.