the advantage of 6 handed is that you can more easily focus on reading the players while with full ring you have to give more attention and it can be confusing
that being said i still prefer 9 handed especially in cash games because 6 handed cash games have less action
The more that I have played 6, 8 and 9 tables. the more I like the 9 persons tables for tournaments. I tend to be more conservative, and I think 6 persons tables favor the aggressor more.
I think the fewer players at a table, the easier it will be for you to analyze each other's play and style of play.