The other good thing about Fast Rent-A-Car is they have locations across the emirates, so if you have issues during a weekend trip to Al Ain, Abu Dhabi or Fujairah, then you can just swap the car out. There can be cheaper companies, but those usually only have one location and are often located in the industrial areas of the city. I rented a car from Fast Rent-A-Car for many months before buying a vehicle here and would recommend them to others. For these reasons, I feel they have the best deals when renting cars in the UAE, especially long term.
Tip: I have also heard of leasing vehicles for 2 years at a reduced monthly cost than buying. If you are coming here on 2 year (or longer) work contract, that could be a good option to save money and not have to deal with selling a vehicle before you leave. The monthly rentals also give a lot of flexibility with leaving on short notice.