I just ordered a Spyderco sharpmaker with the medium, fine, and ultra fine ceramic rods. I know the sharpmaker gives you the option of 30 or 40 degrees (15 or 20) per side. Which angle does s30v steel perform better at? If I use the 15 degree angle, will it hold that edge long or is it better the go with 20 degree and sacrifice some sharpness for better edge retention?