Last summer we rented a car to drive from Vegas to Phoenix. We visited the Grand Canyon, Page, and a bunch of National Parks spending about a week and a half. I was very price-conscious when reserving. I’d considered getting the level that would get a touring Cadillac (which is my car), but I didn’t. Soooooo regretted that. We spent enough time in the car that the extra $250 would have been worth it. So, maybe consider the time you’ll spend in the car when picking one.
Avoid Sixt like the plague.