Good points
Zebedee. To add to
Saucepan man's comments, it does seem likely that Denethor would be a better leader of Gondor in this case. However, the Aragorn-situation would likely have had a similar effect on his decision-making (albeit not as spectacular an influence as the
palantir did). It would not have led to any flaming suicidal leaps (
) from the Steward, but it would have poisoned his relationship with the Wise.