Kefir or Yogurt?

I am basically on an Acne diet and am wondering if kefir or yogurt would cause me to break out since dairy is supposedly bad for acne.

Also, if kefir is good, what kind of kefir should I be looking for?
If, yogurt is good should it be goats or cows.
I know stonyfield makes an organic non fat plain yogurt.
I also saw another company( cant remember the name) and it said unhomogenized on it.
Which of these would be better?

Thanks !!