This article from Roger Clark, a well-respected scientist and designer of image sensors, might be helpful. It explains and visually demonstrates how pixel density, ISO, noise, and overall light sensitivity relate and work:
A couple quotes from your linked author;
"Crop factor and the associated focal length multiplier only affects field of view. They do not affect telephoto reach.
Effective focal ratio is a bogus concept. A cropped sensor does not suddenly multiply the lens focal length with the same f/ratio."
"The bottom line in my opinion: given a focal length limited situation and desire for as much detail as I can get, a camera with small pixels, like the 7D is the what I would choose. Not shown in the test, but given a non focal length limited situation where you can change position to get the subject to fill the sensor, a larger sensor (e.g. full frame) with the most pixels is the what I would choose. But if money were not an object, a compromise pixel size is a good option, if one chooses a high quality sensor like those in pro-series cameras."
Interesting though is his test is on the moon, a rather bland subject. If comparing a good wildlife camera I would think you would want to test with a subject with a bit more color variety and a possibly in the same neighborhood.
Well, the nice thing about a bland subject is the fine details, minutia, are easy to find and compare. In a complex scene of a bird or wildlife or even landscapes, it is MUCH more difficult to make an objective comparison. The moon has very distinct, fine features but is otherwise simple...so the details, and the differences in the details that exist, are easier to pick out. Like the fine differences in detail and color that the 7D picked up, but which the 5D II did not.
Assuming money was no object, a 1D X with a 600mm f/4 L II IS and a pair of Mark III TC's is definitely the way to go. I don't think money can currently buy a better set of gear for a nature fan. But money...well...it tends to be THE object most of the time for most people, and objectively, the 7D offers a lot more than people really give it credit for (especially for a nutty nature fan. )
You did see his degree is in Planetary Science, so no surprise his subject is the Moon.
One of the problems with photographing the Moon is the lack of contrast. For the most part it is a bland flat orb of reflected light. If you are shooting during the early or late phases you can get more shadow for detail. Contrast is one area that the 5D II and 1D IV are much better than the 7D. I have several thousand pictures of the moon on my computer from all three bodies.
I have to discount his comments about loss of color because that has not been my hands on experience.
I don't disagree with his conclusions either. I only say that the margin of IQ between the 7D and the 5D II cropped is very narrow, and not as wide as some believe. From my perspective when talking sensor only, the crop body is only preferred over full frame when you have your longest lens mounted and you have no more focal length.
Well, there are subjective feelings about IQ, and objective comparisons of IQ. Your "feelings" about the 5D II and 1D IV's contrast, at least at the moment, are just that. I was trying to add some objective evidence to the conversation with my link to Roger's article, and I think his evidence speaks for itself.
Regarding moon photography, I too am a moon aficionado. I photograph it all the time with my 7D. Out-of-camera "contrast" is actually something highly dependent on which "camera settings" or "camera profile" you use in your RAW editor. It is also something that is very easy to tweak post-process without any loss of detail. Contrast is certainly not a problem with the 7D, either with neutral white balance, or with enhanced color. All of the following photos, exposed VERY far to the right (so the moon was almost a white disc), looked extremely flat and drab "strait out of camera", appearing to lack any detail at all. I import with the Canon Neutral Camera Profile. With a neutral white balance, bit of exposure tweaking, clarity, vibrance/sat (for the color enhanced versions) and some curves adjustments:http://500px.com/photo/13321795
I'd advocate that much the same information is present in each camera, regardless of whether it is a 5D II, 1D IV, or 7D. Despite higher full-well capacity in the 5D and 1D, there is little difference in actual dynamic range between all three cameras. All three are also 14-bit cameras, so there is little difference in the quantization output. The 5D II and 1D IV probably have a higher gain (more electrons per output level), but all that serves to do is mitigate some of the potential benefits of a higher full well capacity (such as greater ADC bit depth without the need to quantize fractional electrons...the other benefit would be S/N). A higher S/N, which leads to a lower per-pixel noise, for the 5D II and 1D IV is mitigated when a 7D image is normalized to the same size. In terms of pixels on subject in a focal-length limited scenario, the 7D actually captures the most total overall light since the moon covers more total pixel in it's frame relative to the 5D or 1D frames.
I would offer, for the benefit of the OP, that the 7D is essentially synonymous with the T2i (from a "reach" or "pixels on subject" standpoint), as they both use the same sensor.