Nobody is going to confuse a stability ball for an incline bench but you can
easily perform incline bench press on a stability ball provided it is sturdy
enough to support the weight. The Swiss ball incline press works the same
muscles as the incline press on a bench but has a couple advantages.
First of all, since you will be on a ball you are not bound to any
particular angle of incline. This means you can position yourself in the
angle which allows you to target your desired portion of (clavicular) upper
pec muscle. Another advantage is the softer surface of the stability ball
will possibly allow you to retract and stabilize your shoulders more easily
than a hard incline bench.
If you prefer to perform the
incline chest press on a bench there is no reason to use this Swiss
ball incline press but you may want to try it for those situations when you
either don't have an incline bench with an angle you like or simply want to
try other angles. The stability ball incline bench should be one of the
first 2 or 3 exercises you do in any working focusing on the chest muscle