It's a crab shoot on which you prefer.
You shoot crabs down there? Other places it's a "crap shoot".
Quote from source:
Craps is a game in which players make wagers on the outcomes of rolls of dice. Because dice tumble randomly and the outcome is not predictable, craps is a game of chance. From this we can infer the meaning of the metaphorical term crap shoot—that is, a situation whose outcome is not predictable.