There is little difference in IQ for any DSLR at ISO 100. You are buying features and hype.
For landscapes, more MP will give you more detail, but as MP count goes up, so does the difficulty in actually getting that extra bit of resolution. There are some who do very well with high MP cameras, but the average photographer is not obsessed with a incremental increase in resolution, the more important elements such as composition and subject, lighting, DR, etc put and IQ improvements far down the list. In fact, I don't even know how to measure something hypothetical like IQ that only exists in the mind of a photographer and is different for each of them. We can measure several parameters, and they trade off against each other, but IQ? That sounds like something DXO would assign a number to
There is a pretty huge difference at ISO100. That is actually where cameras differ the most since they are all pretty solid at high ISO now. But at low ISO some have one to THREE AND A HALF stops better dynamic range than others. For many scenes that doesn't matter at all, but for many potential scenes it could.
70D RAW file appears to show the same old DR as Canon has been stuck with since 2007 . I hope it is not their new process sensor!
My guess is Canon's noise problems are not really with their sensor, but with the downstream high frequency electronics. In other words, DIGIC. It seems most other manufacturers have moved to on-die processing of some kind...Sony with CP-ADC, and others with something similar...on-die ADC. Canon supposedly had similar technology with the 120mp APS-H (the press releases explicitly called out on-die "parallel image processing", which I can only figure is ADC)...why they haven't put the technology into practice is beyond me.
because they sell cameras and have only invested in 2 fab lines which one is old and can not produce column vise ADC at the sensor = 500nm feature size, which means that it cannot be used for small pixels and =higher resolution with the accuracy needed
120mp is from fab line 2 = the compact camera line where they( Canon) can produce smaller circuits but it takes resources from the compakt line
So it is costs vs better and newer solutions in APS and 24x36
People buy anyway Canon because the brand name is so strong and they think Canon makes the best sensors
And Canon says , Who needs more than 21Mp it is the optimal amount of Mp
No, people buy Canon because they think canon makes the best CAMERAS. Canon DOES make some of the best cameras.
People who don't care about the camera and only care about the sensor buy Sony or Nikon...and when Canon comes out with their 40 or 50mp camera, many of those people will switch (again, or for the nth time), and when say Toshiba produces a better sensor in the future that Nikon uses in the future D900, those people sill switch AGAIN, etc. etc. ad. inf.