I've had stainless, which I hate due to water marks (but didn't care about scratches) and cast iron enamel, which drove me crazy with marks from pots and pans. I know, fussy. I had decided on the composite based on everything that I read here, and then DH decided he wanted soapstone to match the counters. Since that was almost the only thing he asked for in the kitchen, we are going with soapstone. I don't have a functioning kitchen yet, so can't tell you if I will regret it or not. I'm certain the composite would have been perfect.

I love my silgranit. I have not seen their drainboard style in person.

I think your concerns about water marks on SS, and dark marks on ceramic (or do you mean enameled cast iron?) should trump your concerns about a white composite sink staining - that is, if you go with a Blanco Silgranit composite sink and not a brand that may not be as good. Blanco Silgranit in the white colors of "White" and "Biscuit" (a more cream-white) cleans up easily with Barkeepers Friend.

Can you explain why you want a drainboard? I think it limits your options severely. The Blanco with the Drainboard is a very small bowl, so I would not go with that. Alternatively, you can have whatever sink you want and have runnels carved into your counters (do a search on this forum for counter runnels), or, just forego a drainboard. They are a pain to clean anyway because they get the mineral deposits into the crevices and the water marks from whatever is dripping on them (I grew up with one).

What size is your sink cabinet?

Why not have the drainboard cut into the countertop. That would give you a lot more choices on the sink.

I absolutely love my silgranit sink! Best part is the water runs to the drain, it dries quickly and looks SPOTLESS!