give one example there Canons sensor is better
Ok, you like wide DR. I need to shoot at high ISO. If I need to shoot at ISO 12800, which sensor offers a wider DR - the D800 or the 5DIII?
do you understand the benefit and the choiche of underexposure and moving middle grey down 1-4 levels and bring in highligts far above 3.5 stops .
Yes, it's one of several ways to extract the maximum amount of information from a RAW file. But the bottom line is that you can't extract more information than is there to begin with.
Oly OM-D, because DxOMark says it's better than a 7D anyway, right? ) .
OM-D sensor could well be better on some measurements (it's a Sony sensor), but if ergonomics with long lenses, and AF performance are a factor, it's a slamdunk for the 7D. Also, since you mentioned shooting with a 300mm lens -- on Canon, you could shoot with the 300mm f/4, the 300mm f/2.8, the 70-300L, the Sigma 120mm-300, or the Canon 100mm-400mm to name a few. I'm not sure what lens you'd use on the olympus.
Which gets back to other points made in this thread -- the system consists of much more than a sensor.
Exactly. Picking the Civic over the Corvette (was that analogy even in this thread?!?) makes sense if fuel economy or small parking spaces are your biggest needs, picking the Corvette over the Civic makes sense if you engage in street racing, and neither of them make sense if you need to haul your 2-ton yacht to the harbor.
Those of you who defend DxO scores, why do you have Canon gear?
Maybe it's a nuance, but speaking for myself, I defend DxO's measurements (usually), but not their scores. Their scores do not affect my buying decisions because I understand how they generate them (mostly, within the limits of their published methods, which lack some details), and I know how to interpret their underlying raw data for myself and draw my own conclusions based on them. I also use DxO software for RAW conversions (and I'm pleased as punch that as of today it supports the 1D X, because now I can get away from the kludgy DPP user interface).
Some of the reasons I have Canon gear are that they have lenses that better meet my needs, I prefer the ergonomics of the Canon bodies and menus, and I detest the color yellow.