Hey Bobby, I am not Bubba, but, I have some input.
The vertical hanging ovens that are often used in Chinatown are preferred for roasting, as the heat and smoke move along the meat lengthwise, this allows for the convection type of heat to act on the meat. This increases the evaporation of moisture from the surface of the meat. Thus, you get a better surface texture. There is also more even cooking.
Western cooks often believe this allows for self-basting of the meat, this really makes little sense, but, in a vertical oven, you can baste more effectively. When I use to watch the Chinese cooks, with their ducks and roast pork, they would have some poor soul hold a large bowl under the meat, then they would baste by pouring the liquid over the meat. This is partially how they achieve that perfect lacquered look.
A rotisserie rack moves the meat through a heat column, effectively creating a similar convection current of hot air to act on the meat. This eliminates the effect of hot spots on the meat. It also prevents, or decreases the likelihood of scorching on meat, as it moves through both hot and cold areas, the exposure to radiant heat is less focused.
