I've played a few micro-scale Vietnam games. It worked really well for Armored Cavalry type scenarios. That way we had armor (MBTs and APCs), helo's (slicks, scouts and gunships). It really depends on the rule system you use to see if it will be any fun for the VC/NVA player. They tend to be under equipped compared to the Free World Forces.
We use home-brew rules based on the FNG game by Two Hour Wargames. So all the players played the US forces while one person "game mastered" and played the VC/NVA. When the VC/NVA are allowed to be hidden and "pop out" for ambushes and traps it helps to balance out the fire power. Also, once a helo goes down the US mission parameters change from "search and destroy" to "vehicle/crew recovery" and then they start becoming sitting ducks. So there's plenty you can do to keep a VC/NVA player interested.