Anza is generally cheaper when reserved online (no prepay required). But - as many including myself have noted - you can often wait 30-60 minutes for an Anza shuttle from the airport back to the lot. So how much is your time worth - especially when returning late night and you just want to drive home and zzz ??!!

Obviously ParkSFO coupons are a no-brainer, but the best rates will vary depending on the length of your stay. $18 per day is high, $14 is competitive with Anza.
If <3 days I will typically park at terminal but that runs $36/day compared to $20+tax at ParkSFO.

If >8 days then it makes more sense for me to book a car service or maybe rideshare, but YMMV.