it depends on just how tiny your penis is
if you are looking to min-max pick either crossbow or heavy crossbow, arbalest is to situational to play in standard game rounds.
WPF cap on +3 arb is about 185 its not worth investing beyond that unless you are trying to negate weight penalties.
I believe heavy is about 165-175.
Heavy and arbalest are nearly identical accuracy wise. The difference is laughable.