Most notably, the Truman administration was unprepared for the Korean War. American troops arrived with inadequate weapons, equipment, and training, and US war aims were uncertain and less compelling than clear victory. In contrast, under Eisenhower, the threat of US use of nuclear bombs in Korea soon yielded an armistice. Call that inadequate, but it yielded enough security for South Korea to become a free and prosperous nation allied to and sheltering under the strength of the US.
Under Eisenhower, the National Security Council was reorganized and strengthened into a comprehensive system for coordination and advice on national security. Eisenhower's model was his staff system for running SHAEF during WW II. The current NSC system continues on that basis.
As for SAC's practice of flying B-52 nuclear bombers continuously on alert, it was not adopted until 1961 after Kennedy came into office. It was eventually dropped because of the inevitable crashes that risked losing nuclear weapons, spreading nuclear material about, or even having an accidental detonation.
For conservatives today, Eisenhower's flaws and defects loom overlarge because the modern conservative movement was in part a reaction to them. Yet without Eisenhower, the GOP would have likely have faded away to offering only token opposition to expansion of the New Deal. Even a Taft presidency would have been short-lived as he would perished from cancer before the mid-term elections and left the GOP in danger and confusion.
Many conservatives are principle driven to a fault. From the standpoint of the practical politics of winning and losing elections though, one cannot afford to ignore that the public wants help from the government and grants and special breaks when they can get them. Call it socialism and unsustainable, but Social Security and Medicare are near universally popular and have an essential role in the retirement plans of most Americans.
Blaming the modern American welfare state on inadequate opposition by Eisenhower or Nixon or Reagan or the GOPe misses the point that when people are allowed to govern themselves, they usually get what they want. And the American public wants the risks of poverty and illness in retirement mitigated by putting them on the books of the federal government. Eventually, when this becomes financially impossible, the system will be reformed.
A President Robert Taft would've been succeeded by one of the most capable individuals this country had at the time, second in my estimation only to Gen. Patton, and that being his Vice-President, Douglas MacArthur. This country would've benefitted far more from his leadership than that of Eisenhower.