Werewolf or not? Why? Advantages & disadvantages?
werewolf is worth it, the only downside is not being able to get rested (wich isnt that big of deal anyway) and ofc, if roleplay matters, people reactions and comments.
what you get is an incredible damage dealing form, that behaves like dual weilding one handers on steroids, with incredible high stamina regeneration.
becides from the normal and power attacks for each claw, you get a very nasty, even if hard to hit stuff with, sprinting attack that kills most comon mobs.
you do loss armor so you will be very squishy even with the 100 extra health it gives you, but to bypass this you get an aoe medium range shout (use power button) that fears mobs so you can freely slash em up

just dont go for vampirism... really its terrible, you cant fight properly in the sunlight, you get a nasty fire vulnerability AND you have to feed every 2 days tops or everyone turns on you and stuff.
the only usefull thing is night vision... sneak bonus is redundant to any sneak char, and insuficient for any non sneak char, the life drain is too weak to even be worth the time/mana to cast. and the illusion bonus... well thats actually pretty good... if you have illusion leveled and perked as you level, I supose its worth taking vampirism for a sneak illusion using destruction char? weird buildup but meh..