Don't go into it with any expectations..then you won't be disappointed if you don't catch anything..however its more than likely that your expectations will be exceeded!!
If you are looking for big game fish, book the longer trip 6 or 8 hours. Our first mate told us there are bigger fleets taking the game fish closet to shore....so to get to the fish you need to go further out which requires the longer trip.
They tailor the trip to what you want. So if you have children on the trip then they can target smaller fish....if you want to go big, then they will cater for that also. Cant go wrong