If I am understanding your question correctly, the answer would be that the servo arm needs to be at a right angle or 90 degrees from the pushrod to work correctley, in most applications.
This is because if it is not, you will have more travel in one direction than the other.  Most servo arms that have several horns on them are made for that last bit of fine tuning.  Each of the arms is a bit off of center, allowing you to choose the best fitting one.
Ive never rebuilt a servo myself, I ususally just get new ones.  You should have been able to have it end up nearly the same as where it was before.  Possibly you just have something back together one spline or gear mesh off?
As for the best brand, thats highly debatable, ask ten people and you'll probably get eleven answers.  Me, I ususaly stick with a well known brand, like JR, Hightec or Futaba.  Some of the new ones on the scene like Spektrum have some good values too.  I'd stay away from unknown knock-offs but I'm sure some folks have had ok luck with them.  Hope this helps.