Viagra is a vasodilator (makes your blood vessels expand in size) so it isn't just for your cock, some bodybuilders will take viagra before a workout to get a great pump afterward.
You can google Cialis benefits, but its good for Blood pressure, prostate. Long term improvement of general erections and nitric oxide since it stays in your system so long. More frequent erections during the day and nocturnal etc. which in turn over time helps build ur penile strength., Better muscle pumps in the gym.