Counteracted almost completely by the fact that DG members can be VLs though, no?
The Vampire Lord you become from siding with the Dawnguard is NOT NEARLY as strong as the version you become if you side with the Volkihar.
You have to take into account the..
Blood of the ancients..coffin buffs...and artifacts...oh yes the glorious artifacts <3 =P
All of which, the Dawnguard can't take advantage of.
Well they can use the coffins but they don't get the magicka resistance bonus even if they become Vampires if I recall.
If anything siding with the Dawnguard gives you a severely nerfed Vampire Lord and gameplay experience.
People say Dawnguard gets better stuff but all they really get is better crossbows..which is balanced out by Volkihar getting overpowered artifacts and buffs and they of course can get the default crossbow and when you kill the Vampire Hunters in the wilds they have enchanted crossbows and some have exploding bolts.