Hindsight only clears half the picture, because we still don't know what would have happned if Goldwater would have won. Using hindsight, Johnson's civil rights record at least balances if not overcomes Vietnam. Goldwater was scary, even without the exaggerations of the LBJ campaign. With or without hindsight I have to go with the Democrat here. LBJ.
What does 1968 look like if Goldwater is president? The Republicans would almost certainly go with Goldwater. Incumbants always get the nomination if they seek it, at least since the 19th century. Teddy Roosevelt tried to take it from Taft; Ted Kennedy tried to take it from Carter. Both failed. The Democratic nomination would be wide open without a VP Humphrey.
LBJ was a co-conspirator. He took down a sitting president to attain power. I'd vote for almost anyone over him.
Ultimate irony: people who attack historians for being revisionist in respect of LBJ, then in the next post claim he plotted to kill Kennedy.