Hello Imad,
% Complete is the ratio Actual Duration / "estimated" Duration
% Work Complete is the ratio Actual Work / "estimated" Work
They may have the same value if the work is evenly spread along the task.
They are quite different if you assigned only a man at 50% part time during
the first week of the task, and you hurry up with 6 persons full time the
second week.
Gérard Ducouret