You will have more tire size and load range choices with 17" including AS/AT and MT type tires. The wifes 2016 1500 chevy with 17" wheels has any size and tread type available.
I see 1/2 ton owners with the 20" options can't find a good LT replacement other than a high price LT E.
Now if you have a 3/4 or one ton truck the 17" tire sizes don't have the capacity for a 7000 lb rear axle unlike 18" and 20" tire sizes.
There are more 18" tire sizes/load ranges than 20" tires.
Check out 17"/18"/20" tire prices on tirerack.com