By that I mean that I consider good conversion and PP skills to be essential aspects of a professional 'tog's skill-set [...] But here's the bigger point: pixel density doesn't matter. Sensor size is what dictates high(er) ISO IQ (all things being equal, which they're not if we're talking across generations of sensor)
+1 for that - but please don't spread the fact about pp being important, I might try to earn some money sometime with this :-)
Another thing that isn't as highly regarded as sensor size and iso noise is the usability of the body and the on-board software. I'd say it's easier to shoot good pictures if you're not fumbling with your camera and have advanced software capabilities like with magic lantern (which is the reason I didn't get a Nikon).