Depends on how aggressive u are prepared to play.
6 handed sit n gos will see the blinds move more quickly so you have to widen your playing hand range and bet more frequently.
9 handed allows you to be more patient and you can wait for better
hands more than u would in 6 handed.
So I would say profitability ie relative to your style:
Patient style - 9 handed is better for you
Aggressive style - 6 handed is better.