What was one difference between john F Kennedy and Lyndon B. Johnson?

The military involvement of the US in Vietnam was very small under Kennedy, and grew progressively larger under Johnson (a process known as escalation). We really do not know what Kennedy would have done, had he not been assassinated in 1963. Perhaps he would have been just as aggressive as Johnson, or even more aggressive. Certainly Kennedy and Johnson both believed in the importance of opposing the expansion of communism.