I wouldn’t say nothing but to the average person its not going to feel different or make a huge difference in growth. It is supposed to help with the growth of your lower pec area. If this is a weak point then try doing cable x’overs and touching your fists in your waist area.
I have never liked decline bench pressing movements with barbells or dumbbells. I was always stronger declining than I was at flat bench but I never felt like I was in total control of the weight. I tried doing it regularly with dumbbells but I just did not like it. I was doing cable x’overs and decline flies instead of presses to give my lower chest area a workout.
I know that people are going to disagree with me. I have always been a firm believer in heavy traditional lifts for mass such as bench, squat, deadlifts and so forth. I add some isolation exercises into my workout for my shoulders, arms and core but that’s about it.