Is there a web-site where I can look at your friend's photos to check why someone chooses high DR cameras?
He's a wedding photographer, I don't think he publishes his pictures online, he gives them to his customers.
But the usual scenario he was referring to was: very sunny day, bride in shiny white, broom in matte black suit with subtle stripes, anything except his fuji (or, now, D800) will result in said suit looking like a black blotch, and there's nothing he can do about it.
Now, back to the technical discussion...
Let me add a twist: the ADC works linearly, but what you see is log
So, if you have a 14-bit ADC (you can count up to 16384)and can record 14 stops of DR, here is how those values will be distributed:
14th stop: 8192 to 16383
13th stop: 4096 to 8191
12th stop: 2048 to 4095
11th stop: 1024 to 2047
10th stop: 512 to 1023
9th stop: 256 to 511
8th stop: 128 to 255
7th stop: 64 to 127
6th stop: 32 to 63
5th stop: 16 to 31
4th stop: 8 to 15
3rd stop: 4 to 7
2nd stop: 2 to 3
1st stop: 0 to 1
So you may actually have very serious issues in the shadows... which I see in the Canons, but not in the D800!
* if you're going to have issues with "too much DR, not enough gradation", they'll be in the very deep shadows, which you wouldn't see anyway if you were shooting with a camera with the same ADC but less DR; your skin tones are unlikely to land anywhere below the 5th stop fro the top, so for them you have way more values than you need (anything above 50 gradations per stop is usually smooth even after heavy grading)
* how come I don't see this in samples from the D800?