This is why so many pros (and avid enthusiasts like myself) have $30,000 - 50,000 kits. They are exceptionally skilled, and can maximize the potential of that gear.
And Sebastião Salgado or Steve Mc Curry can make a picture better than those, with a used 200$ Canon/Nikon and a bunch of TriX Rolls and a bottle of D76.
Of course, good gear takes the pro a few steps further... but it always comes with tradeoffs or high cost. The RAW Files of my DP3M or a Nikon D810 from a friend are already to large for the daily postprocessing. Or let me say, I would not use the full resolution everytime. But, the drawbacks, like lower ISO (more noise) will be there everytime I use the cam.
If the rumours are true I will like the way Canon thinks about the 5D line... just different sensortypes like the A7, A7R or A7S. So everyone can choose the camera, which fit's his needs best... great times ahead, I think.
For me, the sweet spot is something around 16MP/18MP on fullframe (like the D3s or 1DX), but that's just my opinion.
Btw. the interesting proof for a correlation between ISO and dynamic range is the new A7 II from Sony. Given the same sensor as the A7 had, the DR got lower while the ISO rised up
So, while Canon has better High-ISO capabilties... the DR is lacking. It's a commitment to High ISO, I think. The rest is physics. Giving up the pace on ISO would help Canon to come to the same DR as Sony does, but they don't seem to want this way. http://www.dxomark.com/Reviews/Sony-A7II-sensor-review-Mighty-mirrorless/Sony-A7II-sensor-measurement-Same-sensor-similar-scores