Overview about the main differences between direct path loads and bulk loads.
Direct path load (insert /*+append*/ as select…)

• very fast (especially if no indexes on the target table)
• always loads ABOVE the high water mark, so any existing free space not reclaimed
• locks the object
• you must commit/rollback at completion

Bulk Load (bulk collect into/forall insert)

• fast (better than row at a time), but not as fast as direct load
• can utilise existing free space
• does not lock the object
• additional work can be done in same transaction

Found by asktom.