Almost all males just piss over the side at night. And when surrounded by onlookers in a marina or during the day, you have the option of pissing down the cockpit drain while on your knees in the cockpit. Some use a sink to avoid using the head, but they are in the minority.
good lord man .. at least use a jug inside the boat .. empty and rinse whenever convenient
sometimes the things that may or may not be true are the things a man needs to believe in the most.
Most reasons to consider the choice have been mentioned, but here is one more. Our boat was always cleaner when it was a longer walk down the dock from the sandy parking lot. This was especially true when we had our children aboard.
Biggest and really only problem with mine is I have a rather large power boat opposite me and one over. His big outboard sticks out a ways, right where I'm making my last turn into my slip. I miss him by a foot or so but have to split focus between bow and stern.