Seems like there are four major categories here with a few that are way off in left field. The most common seem to be:
1. One big cover that opens towards the back of the boat.
2. Gull wings that open to the outside of the boat and a center cover that opens to the back of the boat.
3. Gull wings that open to the center of the boat and a center hatch that opens to the back.
4. Two piece hatch that opens to the outside of the boat.
What are the pros and cons of each with ease of use in mind.