FOR many years during the 1960s and 1970s, those guiding United States policy in Africa debated whether the nation's interests lay with African nationalists or with those who would stand with the US in the cold war. Events in October add further grist to the debate. Mobutu Sese Seko, president of Zaire, is in trouble. Isolated on his yacht in the Congo River, he resists political change as looting soldiers create chaos in the country. In neighboring Zambia, President Kenneth Kaunda, defeated in an election, is gracefully entering retirement and the leadership is passing to a new generation. For nearly 30 years, President Mobutu has been a central figure in the implementation of Western policy in Africa. As a young military officer at the time of Congo's independence in 1960, he rose to support United Nations efforts to prevent the breakup of the country. Mobutu was seen as pro-West and anti-communist at a time when the threat of the Sino-Soviet bloc to the emerging nations of Africa was a major concern of Western policymakers. On at least three occasions, the US, Belgium, and France have responded with aid and troops to crises that threatened the stability of the country and the regime of Mobutu. For Washington, Mobutu became the primary channel for the covert US support for Jonas Savimbi in Angola. Although attempts were made to curb the nepotism, oppression, and corruption that marked Mobutu's rule, his value as an ally outweighed concerns over his style of governing. But now, with Cuban troops out of Angola, Mr. Savimbi seeking election in Luanda, and the Soviet empire in disarray, Western nations are concerned with getting their citizens out of Zaire. Ironically, many of these citizens are fleeing to the relative stability of the other Congo in Brazzaville, for years shunned by the US because of its Marxist-Leninist regime. In contrast, in neighboring Zambia, President Kaunda, another of the original post-independence leaders, agreed to an election and has accepted the results. Unlike Mobutu, Kaunda was always treated by the US with reserve. Administrations that concentrated on the communist influence in Africa did not like his emphasis on nationalism, his support for liberation movements and anti-apartheid forces, and his non-alignment. Many factors enter into any comparison between the situations in Zaire and Zambia. Zaire, rushed to independence from the Belgians, suffered from lack of preparation for self-government. Zambia, once part of the Federation of Rhodesia and Nyasaland, had more trained people and at least limited experience in democracy. In the pattern of other African leaders, Kaunda's leadership became authoritarian and his lifestyle opulent. He, too, has left a country in economic decline. Yet he never equaled Mobutu's e xcesses. He saw when the time came to yield to democracy. Throughout Mobutu's rule, the US provided Zaire some $2 billion in grants and loans. This figure does not count what others provided or the costs of the military operations that aided Mobutu in holding Zaire together against separatist threats. (By contrast, US assistance to Zambia totaled only half a billion.) A look at the differences between Zaire and Zambia leads to a disturbing observation. Three other regimes with which we cooperated during the cold war (Ethiopia, Somalia, and Liberia) collapsed into chaos or tyranny. President Daniel Arap Moi in Kenya, another nation close to the West, resists democracy. Nations identified with African nationalism such as Tanzania, Zimbabwe, Nigeria, and Senegal have faced serious internal problems, but, in contrast, today remain reasonably stable. The differences can't be traced solely to a nation's orientation to the West, yet it is tempting to ask whether US attention and support did not enhance egos and blind rulers to their internal problems. For nearly 30 years, Washington viewed Africa primarily through the prism of the East-West conflict. Nonaligned African nationalism was less welcome. The contrasts today between those countries that resisted alignment and those that were identified with Washington raise questions about which stance was be st in the long run for the Africans, as well as for the US.