I try to avoid GC threads as they say the same thing over and over.
North Rim. Some think this is seeing the Grand Canyon. Yes, you can say you have been there but I assure you that you are not SEEING it. You see about 10% of it looking right into the sun.
South Rim. Yes, more crowded; maybe there is a reason that is because that is where you see the whole thing in it's amazing beauty. One end to the other. But you should be there at sunrise and sunset to fully appreciate it from all along the Rim. And you can do rim walks or take the shuttle or drive.
Train ride from Williams. Cutesy I guess, but most of your time will be on the train with a couple of hours seeing the Grand Canyon at midday.
We will be there 4 days again this Fall. And yes, we will also be at Canyonlands, Arches, Capitol Reef and Bryce - we love the National Parks.
To each their own as they say.