Which city you choose to fly into, will depend on the cost of flights, and the cost of car rental, all of which can differ greatly from city to city, and even from different locations within a city. Why not look at Las Vegas, Denver and Salt Lake City.

In the case of SLC, you could make it a figure eight trip, avoiding the one way drop off fee. Probably from Denver as well, although Denver is just that bit further. You would do the northern part of the trip first, and then make your way to the south, calling in on Zion, Bryce, etc., on your way to the Grand Canyon, and finish in Vegas - from where Death Valley can be done as a day trip.

Lifey