Diablo® III

I'm currently at act 3 nightmare mode.

http://us.battle.net/d3/en/calculator/demon-hunter#WRYkcT!Yce!ZZZabZ

I find Bola Shot with the stun ability very useful especially when going against really tough mobs and boss. Could even perform perma stun with another teammate with stun ability

Some might argue Ball Lightning is better than Frost Arrow. This is the case of Normal difficulty. However for Nightmare mode, Ball Lightning is simply too slow when you have tons of mobs rushing at you.

Sentry is to add on to the DPS and Bat Companion allows your Rapid Fire and Frost Arrow to be totally spammable.

Any suggestions or comments on my build? :D

And also I have a question regarding if you choosing Vit or Dex.
I have 2 gloves, one providing 6k hp and 1700 dmg, another one providing 5K hp and 1800 dmg, which one would you choose?

Well the build looks rather fine to me. I'm using a mobile multishot build myself. Though I would go with extra slows on your Caltrops instead of stuns for your Cull of the Weak damage. Otherwise switch out Bola with entangling shot.

The gloves all depend on your current stats.

Are you hp heavy and need some extra damage? or are you a glass cannon and need some health.

Once I got to 10k hp at level 35 with my DH I had to start stocking up on damage gear to switch out myself.

Though you can never have to much health and it is only 100 extra damage.

10k hp at level 35?! Did you sacrifice on your damage? Why doesn't anybody seems to like Bola Shot with the stun ability?

Well people usually use Cull the Weak and that only works against slowed enemies not stunned.

Also I just bought some stuff from the AH and I'm level 45 with 15k hp now.