<Snipped quote by Wraithblade6>
Vampires will take damage in the sun, and are hated if they don't feed for long enough that their stage increases, but become more powerful if they don't feed. They can only feed on a sleeping person.
Werewolves don't seem to have any downsides as a human (I've found), they can shift once every 24 hours, with last 2.5 minutes, and increases by 30 seconds each time they feed. People will attack you on sight in werewolf form.
(Not sure if the same parameters will apply here)
Actually, dependent on your bloodline, ie disease origin with respect to differentiation between Cyrodiilic and Skyrim vampires, vampires have different properties. The Skyrim vampires are generally of the Sanguinare disease and/or of the Volkihar line.
That being said from the lore books on the vampire clans from ESO4/ESO5:
"The Volkihar vampires of eastern Skyrim live under haunted, frozen lakes and only leave their dens to feed. They have the power to freeze their victims with icy breath, and can reach through the ice of their frozen lake dens without breaking it. They are the earliest known vampire coven in Tamriel. The Volkihar vampires are relatively similar in appearance to those of Cyrodiil and they share some similar powers such as night vision, the ability to turn invisible and the ability to seduce others. Certain Volkihar vampires however appear more monstrous than their Cyrodiilic counterparts- some of them have large brow ridges, slits running through their lips, and bat-like noses, and they have powers which aren't shared by the vampires of Cyrodiil—they can reanimate dead bodies and do not burn when in sunlight (although they are weakened by it). The Volkihar have been known to employ Death Hounds as guardians. Some of the more ancient Volkihar vampires such as those of the court at Castle Volkihar are pure-blooded and can even transform themselves into a more monstrous form: the large, winged Vampire Lords which were blessed by Molag Bal himself. This gift grants further powers such as the ability to summon gargoyles."
That being said, they are somewhat more resilient than the Cyrodiilic vampires, which do burn in sunlight rather than become weakened by it. The reversed strengthening is possibly a gameplay effect as well to balance out being overpowered with little risk/deteriment to gameplay challenge, although several mods can reverse this. Although we should be wary to differentiate between in-game effects and lore-based effects such as the werewolf bloodlust being able increase duration of change in a werewolf...
I might go and do a Breton Vampire.