Have you captured an awesome macro photo? Post it here and share the story behind the shot. Be sure to include the Canon gear you used. This photo was captured with a Canon EOS 5D Mark III and a Canon EF 100mm f/2.8L Macro IS USM lens at f/5, 1/160 sec, ISO 100.
"The images from the 5D Mark III after cropping to be the same size as the 7D mark II shows discernable loss of IQ, ..."
I knew you had compared them so I was confident you made the correct choice.
"...your image quality will be so much worse because you lose a lot of pixels in the process of cropping."
You can't say this as a blanket statement. In your case it may be so. Probably is but this is a camera vs camera thing. Sometimes it is good to use an extreme example to illustrate a point. Let's say we use a Rebel Xti and a 5D Mk IV or a 5Ds. Now the cropper isn't going to fair so well is it?
You would have to compare both images in PS at 100% to see if a certain FF is worse with a 1.6 edited crop vs an already cropped image from any certain crop sensor camera. Another factor is pixel size vs pixel density. Sometimes larger pixels trump pixel density.
Viewing a photo 100%, 50%, 200%, or any other “crop setting” is dependent upon the resolution of the monitor that you are using, and the resolution of the image that you are viewing.
Viewing and image at 100% means one pixel in the image is displayed as one pixel on the screen. When I view an image on my laptop, which has 1080P resolution, I see a smaller portion of the image at 100% compared to when I use my 4K monitor, which can display a much larger portion of the image when viewing at 100%.
This observation has made me rethink what cropping to 50% means, or any other percentage for that matter.