Are you doing this for commercial advertising purpose for the dealership? In such a case, the art form is often less important. Black and white is about working with contrast. But you still have to decide if you are making something to meet some other objective, or for the art form. That can decide which picture is the better one. If doing this for a commercial client, then the client decide what is best, right? You just provide the options.
BTW, I'm curious what your method is. What I do is take color images and extract particular colors to represent in monochrome, in some combination (even negative). For people face pictures I start with the green channel as the only source. For landscapes I heighten the red channel.