I think it is a psychological thing. When you nine players, sub-conciously you're mind is noticing only one digit in the number, not two. It's recognizing there are less people to beat. Limping earlier in a hand is less likely to be raised because you have less people behind you, etc. I'm not saying these are valid, conscious considerations to be made, I'm just pointing at the subconsious psychology behind why 9 seaters can often be more appealing than 10 seaters. Which is funny when you consider a 9 or 10 seat table in a 5000 person tourney. But personally, I don't seem to really have a preference for one over the other, and my strategy definitely doesn't change (it's just as bad either way - lol).