This. Sun damage was horrible to work with; besides, any vampire worth their salt would be affected by the sun but wouldn't drop down dead because somebody opened a curtain. They're better than that.

Oh really? http://www.youtube.com/watch?v=E-YBGRT5WJ0. Lol
Werewolves are fine. Totem of the moon lets werewolves summon another werewolf. Plus, their other howls are upgraded to match high level spells and all of their abilities get better.
Problem is, that those Werewolves you summon, are also "squishy" due to having no Armor Rating as well. Plus the Howl has a cool down, unlike the Vampire Lord's "Summon Gargoyle".
From what we can tell Vampire Lords also lack armor, but because they fight mainly from range using dark powers its not as big an issue.
Yeah, pretty much. The Vampire Lord can summon a Gargoyle to tank for him, plus he's constantly leeching health when he deals damage. The Werewolf actually has to score a kill before he can regain health from feeding, and if you got a bunch of NPCs on you, taking the time to feed can get you killed with how squishy you are. Good thing the "Howl Interrupt" was never patched out.
Werewolves are definitely more durable, one thing to keep in mind though is that they are beasts and they deal an incredibly amount of damage when perked. The other thing is that they have some very powerful howls the fastest speed AND most important of all they have incredibly powerful knock downs which affect pretty much every creature in Skyrim even in there current form. I have not come across anything I could not kill as a werewolf even before the DLC perks went in. You have to know how to play as one and think more as a very agile, powerful hunting animal rather than a fully armored dude.
There are some creatures that a Werewolf cannot ragdoll, like Mammoths (Which can pivot on a dime, making hit and runs on them hard) and Dragons. Ever try taking on an Ancient Dragon in Beast Form? With 0 Armor Rating, a single snap of it's jaws will do 300 damage to you...on Adept. 600 damage on Master. Even if a Lvl 81 char did absolutely nothing but devote all his levels to Health, for a total of 900, then went into Beast Form with the Animal Vigor perk for 1,100 Health, he'd still be killed in 2 bites on Master. Even just his wing smashes hit hard. Now imagine the kind of damage that the new "Legendary Dragons" can do...
Makes sense too have no armor rating as a werewolf as well, seeing how your naked in beast form.
In the past TES games however, Werewolves have had a supernatural resistance to common weaponry, only Silver or enchanted weapons could ignore it. In TES II: Daggerfall, Werewolves/Wereboars were completely immune to anything below Silver. In TES III: Morrowind (Bloodmoon), Werewolves also had some resistance to normal weaponry.