I would suggest both approaches to acheive the goal.
heavy weights less reps to build strength and size,
Then, higher reps less weight, less food, to aid in fat loss. and expose the hard work done earlier.
I soppose definition could be built, but that is the hard way to acheive it. If you had a constant total bodyfat, not % but a set Kg of body fat, but increased the size of the underlying muscles, you would get more definition.. as comparably the body fat % would go done.