I would never suggest anyone to go for rent a car. Only if you have an emergency, then rent a car can be considered as an option, otherwise NO. If you look up to their rules book, they are really strict with their claims. And also, If even a small scratch comes on the rent a car, then they will charge you may be double of the original cost. So, rent a car is never a good option.
Switching back in time for saving gas..........! in Dubai............even more strange.
I really dont think that fuel difference will be so much noticeable to support your decision, may be you might save a 100 dhs a month.
If you have any other undisclosed reason for this switch, by all means Qx4 isnt back at all. My friend had it for 6 years and driven over 100k kms without any problem.