Hard to say because JD didn't have much chance to expand or showcase his talent. He was pretty much typecast, as was common in those days.
i am definitely going with my man heath
We got to see more of Heath Ledger's range as an actor, because he had a broader variety of roles. It's hard to know with only 3 popular movies how Dean might've fared with more time.
Both as your talking 2 different time periods and Dean really did not live long enough to show his great potential but both in my view .
Heath Ledger..!! a million times...<3
Heath ledger had more charisma as a person and versitility as an actor..