Arthur can throw only a single boomerang at a time, and must wait it return to attack again. With the powerful armor he can throw two boomerangs and use its magic, which releases five energy waves a short distance in front of him that turn around and fly away, covering a large area behind Arthur.
Lancelot can throw up to 2 boomerangs at the same time. The distance thrown is shorter than Arthur, but this makes then return faster. With the powerful armor he can release energy waves in eight directions.