Thanks for the pix!
Personally, I find Gyllenhaal more attractive, but Ledger will probably get more work in Hollywood. Just looking at those pix shows that Ledger is an "everyman" - he can alter his looks to match almost role offered to him. He didn't come from a family with Hollywood ties like Gyllenhaal whose father is a director and his mother is a screenwriter. Ledger didn't have formal training in acting - he learned the trade craft on his own. He has a long career ahead of him.