I only play Full Ring and have never played 6max. In fact when a 9 seat table drops to 7 players for one orbit, I leave the table.
From what I hear 6max is way more aggressive than FR. I like FR because I play very tight and like to wait for good starting hands and will patiently fold across 4tables over and over. When I am playing well (which is some of the time) I am really waiting for my opponents to play poorly and take advantage of their mistakes.
It sounds like 6max is an action game with more bluffing
, 3betting,4betting,etc. So I guess choosing one over the other would be a personal preference. If you are itching to play and like the adrenalin rush go 6max. If you can grind for hours, go with Full Ring.