Thrifty is the sister company to Dollar. The difference in price is, I am assuming, because they are different companies. I have never used them, so, I cannot comment. They are on the first level of the garage on A&B side, if that is any help. They don't seem to have a large selection of cars, but, you only need one.
I prefer Thrifty to Budget. I have used both and everything about Thrifty was smoother, from checkin to check out. Not that I had a poor experience with Budget, but Thrifty just was better.
I'm going in April of this year and Thrifty has by far and away the best deal again (Premium SUV) $306 for week.