Would you rather pay $1600 for 3 days at Disneyland and 2 at Legoland, OR pay $1300 for 3 days at DL, 1 at Legoland and 1 at Sea World?

Go with the one that includes Sea World. Stay 3 days in Anaheim, and then stay a couple days in San Diego. Traffic in SoCal can suck hard, so don't waste that extra time in traffic. Hotels around Disneyland are excellent when it comes to holding luggage before or after check in. So if you spend 2 days in San Diego, then come into Anaheim for 3 days, most hotels in Anaheim will let you drop off your luggage early in the day so that you can get to Disneyland. Most will even take it to your room when it's ready. Making the drive to San Diego is 1.5 to 3 hours, each way, depending on traffic. It makes for a very long day if you're trying to stay in one place.

And doing a single day at Disney is a marathon, not a sprint. Hit the parks early, get on as many rides as you can from 8:00-11:00, then grab lunch at 11:00-ish. Afternoons are best spent at parades, and moving slowly. You can also do a lot of rides after the fireworks, as many leave the park. Take advantage of Magic Mornings, and Fast Pass. Enjoy a character meal. Goofy's Kitchen in Disneyland Hotel is always good for meet and greets, you don't have to stay there to eat there. Call 714-781-DINE to make reservations for sit down meals, it saves you MUCH wait time, and the sit down meals let you recharge. And you can get free refills on drinks.

Have you checked out CityPass? It's a good deal.

None of the above.

Not really sure how you reduced the cost by $300 by just changing a day from LEGOLAND to Sea World but if those are the true numbers take the DL/LEGOLAND/Sea World trip.

Not only is it $300 less, but you don't need 2 days at LEGOLAND or Sea World.

Now, with a multi-day ticket for LEGOLAND you could go to the Water Park or the Aquarium the 2nd day(unless you have a ticket that allows multiple parks on the same day). But even then Sea World would be a better choice.

You should do the last one, 3 days at Disney, 1 at legoland and 1 at Seaworld. That way your kids get to see all the parks. Also Legoland is very small and you'll be able to see the whole park in less then one day. Same with Seaworld.

I'm an adult so I wouldn't go to a place that caters to children.