Everyone has their own calculus. When I was parking frequently at SFO (and after SFO stopped offering big book in advance discounts for on-airport parking), ParkSFO offered the best price/convenience combination. In terms of freeway access, ease of finding a decent spot, and frequency of shuttle, I found it to be the best off-airport lot at SFO by a pretty large margin. Pricing was also good, if a bit opaque in terms of how the discount would apply.