When I wanted to up my sensitivity i played 2 games on each sensitivity then moved it 1 up and I barl noticed the difference and in an hour or 2 I was playing on 9 (no what I play on all the time).
And I'd just like to make the point, you say playing on a high sensitivity is a disadvantage for snipers, but a lot of snipers will play on 7 or higher sensitivity because if you're trying to follow someone in your cross hairs or in your scope, playing on lower than 7 means when they sprint you can't keep them in sight.