Used to be I too would have said OAK without a doubt. But our little gem of an airport is no longer a great place to fly in/out of. I don't know what airline you're flying, but there are some tricks for avoiding the security lines. Southwest seems to have it the worst, so many people go through the UA terminal and walk to the end to where you can cut over to the SW terminal, avoiding their crazy security lines.

As noted by others, there are many variables, making SFO best at times and OAK best at other times. When SFO is socked in with fog, flights can get in/out of OAK with no troubles. Also OAK is actually closer to downtown San Francisco than SFO is, but if there is an accident on the bridge, that's not much help, and at commute times you can hit some pretty horrendous traffic from SFO to downtown. If you have a good driver, he'll know how to avoid a lot of that though.

I probably only confused you more. In the end, you may just want to go with cost (and cost on rental cars if you're going that route) as it's pretty difficult to predict which one will be most convenient for you.

Edited to add: Don't go all the way back to SFO to rent a car. Driving in San Francisco can be difficult if you're not used to the hills and city traffic, but you could perhaps rent one real close to a freeway on ramp so you can avoid much city driving.

[This message has been edited by letiole (edited 10-09-2003).]