I have never used Dollar. We have used Hertz and did fine with it. They seem to have a good car selection. The nice thing is that the airport is small, so you can get in and out quickly.
Just be aware that car rentals at Rapid typically have capped mileage rather than unlimited. Occasionally, you can get unlimited, but you have to watch for it. I see that right now mileage is capped at 1400.
I didn't fully understand your airport comment. Do you mean you'd rather rent at the airport rather than Dollar, which is off terminal?
You might also try using the Entertainment book for coupons and discounted rates. Others have had good luck getting a cheaper rate through Costco. Good luck!