I know these are great scopes but will some please explain the difference between a VX5HD 3-15x44 with the Fire Dot Reticle and the VX6HD 3-18x44 with the Fire Dot Reticle. What makes the VX6- 6 hundred dollars more besides the magnification? Is the glass that much better? Which ones would you guys chose if you were buying a new Leupold scope