I think a lot depends on your overall style which I guess is reflected in your personality. If you play well with wider ranges then six max is probably where you should be.
Likewise if you handle variance well then you may be able to handle six max. I hate variance (don't we all) although I hate it more than most. Some people just prefer the slower pace of play and FR just suits.
I play FR and have for about four years but I just find it easier to read ranges at the levels that I play than at six max. Also beats happen more rarely in full ring because you are folding more and so it is easier on the old psyche......I think it is easier to tilt in six max and also easier to level yourself.
But if you really have the skills then six max is where you will have the biggest edge in my opinion because you simply get to see that edge more times per hour.
Poker columnist at www.poker.co.uk