Focal Length Preference:
Unlike longer lenses, the differences in focal length between super-wide angles varies greatly with just a few millimeters difference. A 10mm focal length has an angle of view equal to 110°, whereas the angle of a 14mm is 89°, and a 12mm is 99°. This is a considerable difference and one that depends upon personal preferences and usage. Personally, my favorite full frame super-wide angle focal length has always been 21mm, which is the same as using 14mm on an APS-C camera like the Fuji X-series. That said, there are times when I appreciate the exaggerated sweeping effect of something much wider. Nonetheless, in most circumstances I find I can make due with a fixed prime super-wide simply by adjusting my distance slightly.