I found both vampirism and lycanthopy to be pretty lackluster. Turning into a werewolf is pretty useless for me since I prefer spellcasting or using sneak attacks with archery. The inability to become Well Rested however is what kills it. Vampirism however is kind of nice in that I can still get Well Rested and the debuff that happens during the day can be compensated for with the right equipment so its kind like playing with a handycapp.
So, I'd go with vampirism if only because its less useless than lycanthropy and you can get some mileage with Necromage.
I really dislike the Vampire Lord beast form but Vampire is hands down more useful because the beast form is actually more powerful, necromage, character actually gains useful abilities from being a vampire, etc. There's not a lot of incentive to being a werewolf. But I like werewolves better, personally, so I end up going werewolf far more often than vampire.