I grow Brandywine and have had good success, but you're on the right track; I grow way more cherry toms than #4's! I grow using hydro, by the way.

You can grow just about anything you'd like! I help my elderly father every year with planting a variety of heirloom tomatoes, all sizes, in San Diego Country with great success. If you're planning on planting seedlings, rather than starting from seed, why don't you take in one of the Tomatomania sales coming up this spring (tomatomania.com)?
You could also call Laurel at heirloomtomatoplants.com for specific choices. Shes in your neighborhood.

I'm a Orange County native, so have quite a few years of experience with dealing with OrCo growing conditions.

Still not a tomato expert, but here are my thoughts:

Nothing is more discouraging than poor soil, especially clay that smothers the roots if over-watered.

If you have never tried one, I seriously suggest you try making/using an 18 gal tupperware earthtainer. You might be very pleased with the results. My wife doesn't understand why I try to grow tomatoes in the ground anymore.

The container that my wife recommends is made with a circle of strong wire mesh, 3 to 4 ft tall, lined with a trash bag and filled with compost based soil that she buys bulk, $25 a mini-truckload. First year she tried this planter she received at least 100 tomatoes per plant.

Other ideas that have worked well for me are 15 gal pots,I pay about $2 for used ones or new at the wholesale supply.
I drill 1" holes in the bottom (smaller than gophers, you do have gophers don't you?), fill them with container soil and place them on the ground. Container soil gets plants off to a great start, roots gradually grow into the ground over time.

Raised gardens are good, skip the expensive wood sides if you want. If your native soil is anything like mine, you will want at least 50% compost.

On to tomato varieties:
I personally have not experienced the rotting problems you report, so I may be of limited help. Check the posts for blossom end rot (BER). I read, though have not tried using Calcium Nitrate fertilizer.

Large tomatoes often don't set for me, the ones that have produced for me are Supersteak and Ponderosa. I usually stick to small to medium sized tomatoes, early or mid-season. Although we have a long growing season, large, late season tomatoes seem to need warmer nights that I have.
I have successfully grown dozens of varieties of tomatoes,though few have been successful just growing in my native soil.

Have you grown a variety named San Diego? Bred for our conditions and always produces reliably. I just finished picking my last round of Paul Robeson tomatoes, so if you are looking for a long season tomato you might try that variety.

Gary

OC is way too diverse to say for sure. What's your climate like (e.g. coastal, inland, canyon)? I'm in Laguna Niguel (semi coastal canyon) and I've had good luck with Momotaro, Cherokee Purple and Black Plum.