I did a backpacking trip 2 decembers ago, hiking from the south rim, down to the canyon, then back up. I brought a 10-20 and a 70-200 on a crop body. I used the 10-20 70% of the time. Once down in the canyon, I was glad I had the extra reach for the Condors and Deer that we came across. But for being only up on the rim, I think a 17-40/24-70 is more than sufficient.