I usually play crucible and use snipers in my special slot.
I use kontrol freeks, a long one on my aiming stick.
Also I play on a 24" monitor
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Coming from someone who has played competitive shooters on the PC and consoles over the years: The best sensitivity is the one you're most comfortable with. Find one that's right for you in the game your play. I've gamed with people who played both extremes of the spectrum competitively with great success.