Quoteone must not choose which camera based solely on the RAW performance
Why on earth not? If outright IQ is a major consideration RAW performance is the benchmark. Any lens can be made to work on pretty much any camera, but we can't swap sensors.
But I'd love to know the actual real reason.
You underestimate Canon's desire to cripple lessor bodies to protect higher margin products... After how ML unearthed the RAW video performance from the 5d3 that Canon crippled via firmware... this belief has only gained strength. I have no evidence for this specific case, but so seems to be the general trend. Canon will not let you have the best of breed by paying half price.
While I can understand the desire to increase margin rates, they should not be done at the expense of absolute margin numbers. Meaning, what made the 5d2 such a huge success? It was a value proposition. It gave a lot more for the price point than other products (including Canon's) provided on a per dollar basis. And while Canon can think the 5d2 stole some of 1Ds3's sales, why are they ignoring the massive cash stream that the 5d2 generated? The 5D2 did a heck of a lot more to win people over to Canon than the 1Ds3 ever did... in the long term, the halo related benefits continue to give Canon additional revenue despite the 5D2 not being sold anymore... I digress.
Coming back to the topic, my vote goes to coding magic of the RAW files...