As Vael has already answered, there is no difference in stats between a Legendary and an Ascended weapon. They do the same damage and have the same level of bonuses. The main difference is that Legendaries have "fancier" visual effects (such as the skin, footprints, animations, particle effects) and that, when you're out of combat, you can double-click the weapon and select any triple-attribute stat type (Berserker's, Soldier's, Knight's, etc.).
To confirm, compare Zojja's Claymore, an ascended greatsword, from the wiki...
...with a screenshot of my Twilight set to Berserker's stats:
Both do 1,045 - 1,155 damage and, with the Twilight set to Berserker's, add 188 Power, 134 Precision and 134 Ferocity to your stats.