I think you have to toast both. I can only speak for my situation. The artist we are working with is extremely talented not only at design, but listening as well. (Ben Hermance) The reason I say both is he truly uses what the customer likes/wants (listening) and puts that together along with his touches to come up with a final product. So in alot of cases it is a team effort. I am sure there are times when someone say here's the car I have, go to it. Ben also does cars on his own. You can see some on this sight. These designs are his alone, but thay all have to be built. You then have to look at execution of the design. This is a team effort as well. A builder can only truly reproduce the design if they are talented enough and if the design is capable of being built. Alot can be put on paper that will be dang near impossible to make work in the real world. So in the end for a complete car, rendering to finished piece I think it is truly a team effort. JMO
By the way I used Ben as an example because we are working with him. All the artists on this board are extremely talented. Maybe some of them will give you some input.
Later,