I know there is the Silver hand but are there any others? Just became a werewolf and this time decided to just leave it as is, as in not kill anymore silver hand after that one mission, so say if I become a werewolf in town, and leave after people see me which gives me a bounty, if I do that enough times will they call in werewolf hunters on me?

Same goes with being a vampire, if people know I am a vampire than why has no one sent a vampire hunter after me?!

Where is the awesome points that make it accually a challenge to be either or of these creatures?

nope and nope.

There are a group of people who kill daedric worshipers and undead, I believe that they are called "Vigilants of Stendarr" or something close to that. They might attack you if you go to their base.

Well, I am not sure if the Vigilants of Stendarr will go after you considering your not undead. Though we can just use general assumption and say they are; thus giving you an excuse to warp into a werewolf and eat their faces possibly?

Well, I believe that they hate anything "unnatural" so that would be vampires and possibly werewolves, and being a werewolf kind of assumes that you have something to do with Hircine. And yes it would.

side note: Do they actually do anything? I went there once and they just sat around their building/base.