You can add my experience with the staff at this park to the others on this board. That is, the staff at Zion Canyon Campground & RV Park is rude and most unhelpful. They really do need to find another profession. I highly recommend finding another place to stay if at all possible.
After dealing with the private campground in Springdale, we were most please with the facilities at Watchman. Sure, you only have electric but that is all we really need. There are no showers in the campground so you need to shower in your RV (though several private places in Springdale advertise showers for a fee, none were open on Sunday November 1st or, in the case of Zion Canyon RV Park, were closed for the season. Being in a national park, Wi-Fi is also not on the menu but you can get internet access at a decent speed if you have a Verizon data plan (I don't know if ATT serves this area). For the location and price, you can't beat Watchman Campground.