I used to play on Ten when I was a quickscoper on Cod4 and Mw2.. but every since Black Ops I've been playing on Five because it's much more accurate! I used to think that the higher the sensitivity you play on the better you are.. I realize now that anybody that thinks that is obviously dumb, because all my "MLG" play on medium default sensitivity. The only people that think playing on 10 makes you pro are the L33T Trih3rd 360 n0 sc0p3 b0om h3dshotters in S&

with names like xXx03IQu1kSc0p3Pr0xXx.
You're better off playing on a lower sensitivity it's better for you accuracy and it's better for those long range shots. I remember when I used to play on 10 my accuracy was always below 15, but ever since I switch my accuracy has been in 20s. Also, 5 is perfect because it's right in middle, it gives you just enough time to hop around and kills those guys shooting behind you and it also gives you the good aim for those long range shots. It's perfect.
But then again it's all personal preference!