I used G6 blades on my 48" Tiger Cub for one season. As they are heavy, the blade tip speed was slower and if an unmovable object is struck, the risk of more serious damage is possible. I was more comfortable with actual G5s and still use them. I know that Oregon has made some changes in their aftermarket Gator blade lineup. The label on my latest G5 blades said that these blades replaced the former G6 blades. These blades are narrower and thinner than the G6 blades that I have used in the past.
There are many factors that affect mowing results. Type of grass, moisture content, operator technique, ground speed, width of the cut, amount of the cut, blade tip speed, pitch of the deck. Generally a correctly setup mower deck has a 3/8" lower blade tip height with the blade forward. However there some grass types where having the forward blade tip height higher provides a better cut quality.
A Scag Liberty Z has aluminum spindle housings with a blade bolt that threads into the spindle whereas higher level Scag machines have a cast iron spindle housing and a 5/8" blade bolt that passes thru a heavier spindle and held in place with a locknut above the drive pulleys.