Always learning me - I've used fan and pencil and like both for different brushes/jobs.
Pencil = accurate when trying to avoid overspray. Brilliant on windows with problem frames/seals (old ali, georgian, vents in the middle etc)
Fan = good for quick coverage on upvc commercials.
Best of both worlds for many jobs? Peter Fogwills Salmon with stainless steel light fan spray to the sides only (no upper or lower field of spray)