I'll attempt to give the answer that wmchauncey is looking for.
All cropping reduces the potential resolution on the print. All wide-angle lenses reduce the potential resolution of specific features on the sensor.
When taking any shot from a given position, the trade-offs are; fewer features with greater resolution, more features with less resolution, assuming one is using the same camera and assuming you have a choice of lenses.
This is basically one of the reasons why some photographers opt for a larger format camera.
To make the most of your camera, whatever its pixel count, you should try to select the appropriate lens for the subject (composition) in order to reduce cropping to a minimum.
The necessity for cropping should only arise when the aspect ratio of your composition differs from the aspect ratio of your sensor.
Zoom lenses are popular because they allow a more precise match which results in less drastic cropping.
On my 12.8mp 5D, with just 3 lenses and a 1.4x converter, I have a continuous focal length ranging from 15mm to 560mm. (If only that applied to the rest of my anatomy. Okay! Only joking. Please don't ban me ). I'm rarely stuck for an appropriate lens, although, of course, I would like to extend that range beyond 560mm if it were affordable and pratical regarding weight considerations.
Extending the range wider than 15mm could also be useful, but is also problematic for reason stated above. The greater the number of features, the lower the resolution of those features.
In situations where extremely wide panoramas are sought, which would involve heavy cropping of the height of the image, it's better to use a good stitching program like Autopano Pro, which can often produce perfect stitches of hand-held shots.
Have I answered all your questions, wmchauncey?