You need to describe the design of both stucco system and your wall system in great detail in order for anyone to answer your question. Pay close attention to tne differences in material composition. This may only be a synthetic top coat, or it could be two very different systems.

Thanks, Mightyanvil.

According to our contractor, the more expensive has some plastic bonding stuff mixed in that makes the stucco more watertight and less likely to develop cracks. It is difficult to tell what else is different from the brochure: they talk about acrylic modifiers and bonders to improve tensile strength.

Thanks for comments!

I'm in Marin and we've done the same thing to our house. We're looking at DryVit topcoat all over the house, old and new. They can create any BM color so that's what I'm working on now. You can also pick the texture you want and of course the texture that I like is the fine Sandblasted finish which is more than the rough walls. Ask your stucco guy about DryVit and see what he says. Sorry i don't know more about it.

Another option I've just heard about is non-colored stucco with an elastomeric paint top coat. This is a very confusing choice to make

Ive been told that the elastomeric paint is not the way to go. It is less expensive but looks "plastically" and more industrial. It's shiney.

I guess it's your call but it sounds like overkill to me. I've had two different stucco houses in So. Cal. over the past 30 years and have never had a cracking problem with the stucco. The few hairline cracks that I've encountered were very easy to patch and touch up to match the house color. My guess is that if you have a serious problem that causes anything other than hairline cracks, even the more expensive stuff will crack. As far as being more waterproof, stucco is installed with black paper behind it and weep screeds at the bottom to allow any moisture that penetrates to escape. So that sounds like it's trying to cure a problem that doesn't exist. Just MHO.

We have the same choice. Because we are building in the sierras at 4500', the choice is clear. What your stucco contractor is refering to is an acrylic top coat, same /similar to dry vit.The advantages are with extreme temperature changes, the top coat has flexibility to expand/contract, reducing the chance for cracks. The flexibility also is an advantage because of the ground movement that californians have come to know and love,(dont know about that love part).The other advantage was mentioned by another is that it can be mixed with any color spectrum ,as the mix is liquid form,compared to the standard color choices offered by the powdered color mix.In the bay area, you should be okay with the traditional tried and true stucco, but for peace of mind where we are building, we are going with the acrylic top coat and a three coat system as there is a two coat application offered.The two coat application is simply a lesser thickness of the scratch/brown coat. The scratch/brown coat is applied, allowed to set for a time for curing and cracking,then the top coat. The three coat is scratch coat applied, sits for awhile, brown coat applied, sits, then the top coat.The three coat system is a little more structurally sound, you might want to run this by your contractor as well.

Hardie make a siding that mimics stucco.