T.F.
We use Thrifty but, we have a corporate account linked with our company. We have Corporate accounts for hotels as well. Hubby dies the traveling and I do all the financials, travel arranging, etc.
I personally do not use discounters for anything.
Don't sign up for the extras offered, especially insurance. Your car insurance will cover you if there is an issue. Make sure you get unlimited miles and drop off at the same location as pickup.