I too am a Delta/Marriot snob, but use Hertz as being a DM gets me Hertz elevated status and perks.
One of them is the extra miles when booked through Delta.
The rates are usually good (80%), so I'll check other companies on the Delta site as well as independently.
But using Delta, gets me the extra miles, and with the elevated Hertz status, I can select a 'standard' car, but when I walk onto the lot, I get my choice of Presidents Circle cars, which have been almost always very nice upgrades.