These are the pro's and cons as I see them. Myself Just My opinion.
Full deck pros:
Less likley to be swamped when entering the water from a steep bank, our tipping a gunnel, and swamping the hull. Much harder to sink.
Adds rigidity to the hull structure.
Does not collect trash, and grass when running in rank vegetation.
Easier to walk around on when getting on and off of the boat.
Looks cool.
Full deck cons:
Heavier and more $$$$ than the same hull that is constructed with an open top.
Less convenient hull storage size wise, but stuff you put down there won't blow out.
Harder to repair hull damage, fix a fuel tank problem, or replace polymer.
All will probably require back deck removal on most full deck hulls.