User blog comment:Nerakil/Did you prefer the Dawnguard faction or Volkihar clan?/@comment-3492791-20121212044854

Not trying to spoil anything, but just pointing out that the sun will become less of an issue for you by the end of the questline.

For Volkihar, the bonuses you get, as you'd imagine, make you a better vampire. Such things as the blood chalice thing and the Vampire Lord bonus equipment. For the Dawnguard you get a bit more. You get three new spells that do damage to undead (and only undead), some magical runed dawnguard equipment that makes for better vampire killing, and the crossbow and it's upgrades.

The reason the crossbow may seem lackluster is that you only have a V.1 crossbow. Via the Dawnguard you can improve it 3 times to do more damage and ignore 50% of armor. You also get magic bolts that do extra fire, frost, and shock damage depending on which you use.

As for the Vampire Lord, it is actually incredibly powerful, but for whatever odd reason Serana neuters you. While Serena is your follower your drain health spells is heavily reduced in damage. I'm not really sure why this is (although I do have my suspicions), but after you finish the questline and can be rid of Serana, you can decimate people with the vampire lord.

As for personality, there are the three people you recruit for the Dawnguard (I can't remember their names atm) that are pretty fun to listen to, and there is Irsan, who is the biggest buzzkill since Buzz Killinton, but every one else in the Dawnguard is just kind of, there. None of them really have any personality at all. They all seem like they are there for no other purpose than making the Dawnguard seem like a bigger group. One of my grievances about it was that the kid you meet when you are going to join the Dawnguard. They were setting it up to be like he was going to be your friend, perhaps an equal that you could progress through the Dawnguard with as sort of a reference to see how fast you were doing it and support you. But literally as soon as you return to the fort after rejecting Harkon he's a full Dawnguard and doesn't even remember you. It's...disappointing. Nearly all the vampire's have personalities, but as you've already found it's usually just "snobby superiority".

Ultimately, other than what I mentioned, you get the exact same stuff either way. I would suggest doing both factions on different character just for perspective, but unless your main is a vampire I would suggest the Dawnguard for it, because even as the Dawnguard you can still get Vampire Lord.