I chose my Sightron 4-20 x 50 because I like to do some offhand shooting. That is a bit more difficult with a 6x IMHO.
Sightrons website also stated the parallax could be adjusted below 20 yards. This is what I wanted for the 20 yard indoor range.
I wish all optics manufactures would put this information on their websites.
I purchased mine from Hirsch Precision. It's now mounted on my CZ 452.