I prefer 6 handed ring games, and I prefer 9 handed for tourneys.
Here's my reasoning behind that.
In ring games you're strong hands have a better chance of holding, and you can play medium hands a little more often because no matter what position you're in there aren't that many players to act behind you. Also if you're on a draw and feeling like trying to draw out you have a slightly better chance that the card you need hasn't been folded already.
In tourneys the blinds obviously rise, so to have 9 players rather than 6 players give you a great advantage. No matter what type of player you are the blinds won't hit you as many times giving you better opportunities to pick up chips. I also enjoy 6 max MTTs too just as long as they're not turbos, and I start with at least 3K chips.
That's just how I feel about the matter.