As a Vampire Lord:
You can hover and glide with wings that emerge from your flesh, you can slash at your enemies with razor sharp claws, you can turn into a swarm of bats and teleport out of danger, you can levitate enemies as you drain the life from them, you can summon gargoyles to fight your enemies, you can take the very souls of your enemies and turn them into a legion of undead minions.
As a member of the Dawnguard:
Um, I guess you could use this crossbow?
Wonderful! Finally I can use a bow in one hand, while using a shield, sword, or magic spell in the other hand! Thank goodness, I've been wanting this since the game was released!
Well, actually the crossbows are two-handed weapons.
What? We already have two-handed bows. Why would you do that?
Okay, but they do have their own perk tree, right? At least we'll be getting some fun new crossbow perks.
Actually, it just uses the existing archery tree.
Seriously, in terms of new features and gameplay elements, they can't possibly have allowed the two new factions to be THIS unbalanced, right? There have to be some other features that they're just not talking about right now, right? As a good character who is a level 100 archer, I feel like I have almost nothing to look forward to other than the story and setting.