Optical clarity, IMO is much more subjective than most people realize. Scopes that in a price range are going to compare in clarity as other scopes in that price range. For example, I would have a hard time telling which scope is going to be superior when comparing say the Vortex PST 6-24X50 to the Sightron SIII 6-24X50. There will be a difference when comparing say the Sightron to a Schmidt and Bender.

As far as warranties goes, I've never had to send a higher quality scope back to get work done on it. Go with a reputable brand and you'll be okay.

Carefully consider what kind of shooting you intend to be doing with your rifle. The type of shooting will determine what kind of scope you're going to get. Go with your gut and start shooting!!