I agree with Craig -- all things being equal, I'd rather fly from SAN. It's a much smaller, easier to navigate airport. But, I've used LAX many times and have never found it to be a particularly difficult large airport to use.
But there is almost never a situation where all things are really equal. Here are a couple of considerations.
I assume you're renting a car. If either airport would cause turning the car in at a different location than you rented from, you'd better to check to see if there would be any additional cost. I've done that with no extra cost, and I've researched rentals where the difference would have been as much as $400 -- for the same dates, same airports, different rental companies.
The other consideration for me would be whether the entire trip would be more or less convenient. For example, if you're connecting, how are those connections? Would one option have better, more attractive connections, or would one be unreasonably bad?
Lots of thing to consider besides just price and departure time.