Hi, for me powerbox is best choiche. Central screw is easier and quicker. No problem with interchange of fins. Two years ago I hitted a rock hardly with a Select 48 Course, head broke, screw curved, but BOARD FINBOX SAFE! I've heard about tuttleboxes broken in similar situations: two thight and hard connection system imho. You save the fin but loose the board, finbox repair is an hard and pricy one!
But: first of all now if I sail in rocky spots I use a longer powerbox fin with a thick rubber spacer (1 cm) under the screw head, so now I have a "fin bumper". Second I was wondering about a cave screw with inside a safety leash (a fishing rope) or something similar to avoid loosing the fin in case of impact (easy when yore trying to ride waves near the shore)...
Nico, Venice, Italy