Yes, I understand that a lot of it is subjective.
I wasn't speaking about subjectivity at all. My two points were that A) the 5D3 sensor objectively measures better across the board, but that B) literally dozens of variables that have nothing to do with the sensor could cause a 1D4 RAW file to look better then a 5D3 RAW file.
People fail to realize how many links in the imaging chain are an order of magnitude more important then the sensor differences they endlessly ponder and debate, even FF vs. crop vs. 4/3.
I use Canon DPP to view, straight out of the camera. It is set to "fit to window", so the 1D IV images are the ones being magnified.
To give you an idea of the variables and tolerances: what you think gives the 5D3 an advantage might in fact give the 1D4 an advantage. Even Photoshop uses fast scaling algorithms for screen display that can look worse at certain magnifications. An even better example: Apple's Preview is notorious for destroying images at certain sizes. You can open an image in Preview, it looks horrible, then click full screen and it can grow by maybe 15% but all of a sudden look like gold. Or vice versa. I don't spend that much time in DPP, but it wouldn't surprise me to observe the the same.
And opening both in DPP with "neutral" settings does not eliminate settings or profiles as a variable. DPP is doing different things for different cameras even if all the human visible settings seem the same.
I can compare it to listening to different audio amplifiers. The specs may be the same, but they sound different.
Bad analogy. There's a lot of nonsense that gets passed around the audiophile crowd, and I rarely ever trust a claim unless it's repeatable under blind testing conditions.
I guess what I'm getting at is that you're claiming a camera which objectively tests worse (though still very, very good...none of these cameras are ever "bad") looks better then one which objectively tests better. If you want to know if something is wrong in your 5D3 imaging chain, post RAW files (identical subject / lighting / lens / exposure).