The incline press targets upper chest better than flat bench because the 45-degree angle forces you to stay strong through chest, shoulders, and triceps. Most lifters need more upper-chest development anyway.
The reason why I specifically like an incline press over a flat barbell bench press for building muscle is a number of reasons. The first reason is most of the time guys need more upper chest development, and the flat press, yes, you are going to develop muscle on it and you can use more load on a flat press. However, you can get away with using a lot more load if you know how to set yourself up technically on a flat press. Here, this exposes you. An incline press absolutely exposes you at a 45-degree angle. You have to be strong through your chest, your shoulders, and your triceps because of that exposure. You're not able to get into the same position that you are on a flat press.
