Converting sensitivity is all about making the camera respond in a way that you expect. If you are expecting a very specific wrist flick to always make a 90 degree turn, then you would want to use the 360 distance conversion. If you expect it to always rotate somewhere close to the edge of the screen, then you use a specific monitor distance %. I personally don't think this way, and I want the turn amount to scale by the actual change in the image that I see when I go from hipfire to ADS. If I see the image change by a factor of 2 when I rightclick, then I'm expecting the turn amount to scale by a factor of 2 as well. 0% is going to give me the sensitivity that I am expecting.
The other matches only help preserve a very specific characteristic. So I don't bother with them. People probably use a specific distance % at first for the sole intention of matching a distance, but then it later becomes a matter of picking a % that gives a certain speed that they like. After all, the distance % only works between 2 points, no where before or after, and only purely vertical in 100% of cases, and horizontal in a niche case. Diagonal doesn't work because the pitch of the camera affects the yaw, and at a high fov, diagonal movement within your view, is creating a much larger deviation in pitch compared to a low fov.