I do not want to digress to a NR - SR debate once again on here. But the NR you see about 10% of the Grand Canyon, it is very isolated, and any photography is shooting right into the sun. Oh, no hookups in the RV park. Like I say, you can say you have been to the GC - but you have not SEEN it.
Zion is beautiful; no question. But you ride down the canyon in a bus and get a heckuva sore neck constantly looking up. Bryce you drive to places, are looking down and really great hiking. But both are very different from each other.
We will be back to Bryce for photo work this fall again - as well as Cap Reef and others. But will not be going to Zion.
To each their own.
To first time, and maybe only time (we have been to both lots but only 2 times to the NR as we went back thinking we missed something and realized we had not) to GC, I recommend the SR to get the full content of it.