Rental car or taxi?

Planning on a long weekend in November.

No real need for a rental car. But a few weeks ago, I found rental cars for $US2/day from Payless and a bit more from Europcar. Now it's more expensive, but still only $25US to rent a car over several days. Given that the airport taxi costs about $20USD one way (and much less on the way back)... does it make sense to rent a car? What's the hassle factor getting in/out of the airport, gas (I've bought gas elsewhere in mx, and the attendant kept the change as a 'tip'), parking, etc? Vs the benefit (how's parking in, say, downtown Zihua)?

Of course if the exchange rate crashes any further, the taxi is the obvious option.