Small Recessed: Metal recessed handle with plastic dish.
Large Recessed: Large metal handle with D-shaped metal dish.
Folding: Metal handle that pulls out for carrying and folds flush when not in use.
Routed: Weight-saving (but labor-intensive) alternative to hardware: handles are routed directly into the enclosure. With an Okoume build you can save 3+ pounds of weight over the large "D"'s
None: No rigid handle.