Well considering werewolf (in my own opinion) is kind of useless and you're a sneaky dragonborn I'd go vampire lord because you get the buff of champ of the night and plus the didnt really do a whole lot with the werewolf perk tree where the vampire lord tree is awesome. The werewolf is still only a once a day thing where the vampire is as often as you'd like. yeah betraying the dawnguard hurts some but just wait till the end to get all of the benefits from them.