I am by no means an expert of this subject, but I can tell you from experience that I did notice a difference in chest appearence by changing from incline to decline to flies. I had more "cleavage" from doing flies and the bottom of my chest got bigger from decline and the top got bigger from incline. I took about five years off because I did not have time to go the gym. Now I only have access to a chest press machine and my chest looks completely different.