The "number of photons collected" is the critical factor. (In fact, I feel an intuitive resonance with this claim although I couldn't support it logically). I recall reading somewhere that the further right one goes on the histogram the greater the number of photons one will collect. The author divided the histogram into thirds and stated in support of ETTR that something like sixty percent of photons collected are available to the right hand third and only ten percent in the left hand third. I drew from this that even though the DR of many of the subjects I shoot is two to two and a half stops, I would benefit from ETTR because I collected more photons. I'm certainly over my head in this discussion but I sincerely want to capture photons to my best advantage in making prints.
For the smoothest and cleanest image the camera is capable of, one should ideally strive to capture as many photons as possible, consistent with an oppropriate shutter speed and aperture, and without blowing any of the channels.
However, there are lots of trade-offs and compromises on the technical side of photography that one has to deal with when the camera is not used in fully automatic mode, so one should try to be aware of the significance of the effects of any settings which may not be ideal as a result of the requirements for the circumstances and the lighting conditions.
That is why I recommend experimenting with different settings, different exposures through autobracketing for example, to see for oneself what effect an underexposure of 1/2 a stop, or 1 stop, or 2 stops or more, may have on the quality of certain parts of an image using a particular model of camera.
Because I'm a peripatetic type of photographer, I don't always have the time to prepare each shot for a perfect ETTR, nor the opportunity to retake the same scene if I got it wrong, so I'm very attracted to the high-DR characteristics of the D7000 which allow me to underexpose an image at base ISO by at least one stop, and maybe as much as 2 stops, whether by design or accident, and still achieve image quality in the shadows on a par with an ETTR shot of the same scene using the equivalent Canon 60D.
Comparing the D7000 at 1 stop underexposure with the 60D at half the shutter speed (double the exposure), I would not expect to see any image quality advantage in the 60D image in any respect, whether in the deep shadows, moderate shadows, midtones or highlights, with regard to DR, SNR, tonal range or color sensitivity. Slight differences in resolution due to lens quality, AA filter characteristics and sensor pixel count is another issue.
A two-stop underexposure comparison would be interesting because theoretically shot noise in the shadows of the D7000 image should then be greater, and SNR in the midtones might also be noticeably worse.
On the other hand, the advantages of a 1/100th sec exposure with the D7000, as opposed to a 1/25th sec exposure with the 60D, could be of far greater benefit than the disadvantage of a barely perceptible increase in shot noise or a barely perceptible reduction in SNR in the midtones that might only be apparent at 100% on the computer monitor, representative of a huge print of around 6ftx4ft.