User blog comment:JAlbor/Dawnguard: What Everyone Should Know/@comment-4324788-20120630234138/@comment-5915494-20120702121418

Just because you receive a few dozen steel bolts and a low-end crossbow does not instantly remove the Dawnguard under the guise of uselessness.

I for one joined the Dawnguard as they offer me the best services attribuited to my playstyle; combat orintated items and followers to say the least. The crossbow itself is only one aspect of the faction, a minor one at that, which can be upgraded through the quest Ancient Technology to a Dwemer Crossbow along with multiple bolt variants (ice, explosive, shock), all of which you cannot obtain through the Vampire faction questline.

"Dawnguard Vampire Hunters will find you and attack you like the hired thugs" and the Vampires will not? I found on multiple occasions a few gargoyles, death hounds and master vampires can be devastating to an ill prepared player, in comparison to the Dawnguard's close combat weaponry which can easily be dispatched (the disarm thu'um being the most practical here). Both factions will attack you "like hired thugs", even in towns or cities, but it is the Vampires which cause the most grievance through debiltating effects, dots and long ranged coined with close combat attacks.

The ending to both of these questlines has minimal difference. Siding with the Dawnguard results in you assaulting Castle Volkihar, whereas siding with the Vampires results in assaulting Fort Dawnguard earlier on. The assaults are built with the faction in mind, the assault on the Castle is close quarters (which suits a Dawnguard, combat orientated player) and the assault on the fort is longer range (which, in turn, suits a Vampire, magic orientated player).

It is certainly not just who gets the shinier loot for how you play out the quest line, it is based upon your current play style (whether it be magic or combat) that should affect your final choice. If roleplay is a factor here, go with your major roleplaying aspect, so good characters would side with the Dawnguard and evil characters would side with the Vampire Lords.