We went to the Grand Canyon once and found the tour prices to be high. Instead of a tour we ended up renting a car and getting a room just out side the park for one night. The cost ended up being about half of what a tour would have cost for the 2 of us and best of all we were on our own time. Ended up hiking for the afternoon and getting to watch the sunset and then getting up early and hiking again till about noon before we headed back. I'm sorry, I couldn't answer your question on best tour, but wanted to offer another option than the tour.
There are coupons out there for tours to the Canyon so that might be an option. Try vegasforlocals.com and keep an on travelzoo as both have offers often.