I always go with National or Enterprise (or Hertz/Avis if I were a couple of years older), even if the no-name brands are cheaper.

National's Emerald Club saves a ton of time since I can bypass the long lines at the counter and go right to my car. And their vehicles are all relatively low-mileage with no body damage.

If National is very expensive, Enterprise is usually cheaper, and I've had good experiences with them other than a hard-sell on the insurance, which I just refuse since my credit card covers collision damage and my personal insurance policy covers liability.

I've had great luck playing the upgrade game with Enterprise; I always book an economy and usually get at least a midsize for no extra charge (after having been offered to upgrade for $10/day) since they don't keep many economy cars on the lot.

Another advantage to Enterprise is their numerous off-airport locations in most cities, which can be used to avoid all the ripoff airport taxes and fees. And most locations don't assess an extra underage fee for renters ages 21-24.

The "not exactly" chains (as Hertz would say) such as Advantage, Payless, Fox, and Thrifty are mostly franchised so service and vehicle selection is very inconsistent. National and Enterprise are primarily corporate-owned, which ensures a smoother rental experience nationwide.