What was the main Military Helicopter used in Vietnam and why?

The UH-1 Huey (built by Bell Helicopter), officially called the UH-1 Iroquois helicopter. With the exception of the AH-1 Cobra; US Army choppers are named after US Indian Tribes. Over 5,000 UH-1 (Utility Helicopters) were used in Vietnam, nearly 12,000 helicopters total combining other types. Of those 5,000 Hueys (a slang term derived from the letters U-H), about 3,000 were destroyed in Vietnam. However, about 8,000 Hueys were manufactured. The Huey performed more types of combat than any other bird...medivac, gunship, troop insertions, re-supply ships, SAR-Search and Rescue...to name a few. Other birds used in Vietnam, but not so famous: 1. Kiowa (civilian version is the jet ranger) 2. Cayuse (flown in TV series PI Magnum, starring Tom Selleck, in the 1980's) 3. CH-47 Chinook (twin rotors on top, ramp in the rear for cargo) 4. AH-1 Cobra (US's First factory designed/built attack helicopter) 5. CH-53 Sea Stallions 6. HH53 Jolly Green Giants