More than that it depends on what type of pistol shrimp you are wanting. A caribbean will likely eat the cleaner as they are a natural prey of the caribbean. A tiger on the other hand should be okay provided the tank is large enough and they are both well-fed. I personally would get a cleaner and forget about the pistol. Just my 2 cents.
EDIT: Actually given your setup I would get a pistol and forget the cleaner but still, that's me and it isn't my tank lol. Good Luck.