It's not about turning in a circle. If you turn the mouse slowly, you'll move at one speed. If you turn the mouse faster, you'll turn slower.
Looking at
this thread, it seems negative mouse accel is tied to mouse smoothing, so if you have a higher mouse smoothing, you have laggy input, but less accel. If you have lower smoothing, you have more responsive movement, but weird negative accel. You're pretty much stuck with crappy aiming no matter what. Maybe you just have a fast enough computer that the mouse lag isn't as bad.