XF 70-300 is best followed closely by the XF 55-200 then the XC 50-230. Of course there is the XF 100-400 but I get the impression that is out of your budget. The XF 70-300 works with teleconverters the 55-200 and 50-230 are not if that is a consideration.
I'm not sure what qualifies as "best" because there are many variables involved in all three consumer Fuji variable aperture lenses. If weight, size, overall zoom span (5.6:1) and quality of bokeh are your highest priorities, the 50-230 is actually pretty far ahead on all those counts. If speed is the main concern (they are all pretty slow), the 55-200 wins (by about one-sixth of a stop) over the 75-300 with the 50-230 trailing by a full stop. Sharpness and reach goes to the 75-300, but the bokeh is rough in many situations unless you stop down.
If the light is good, I'll be shooting with the 50-230 if I don't need the extra reach because the rendering is so much better than the 75-300 - and the sharpness is not that much better with the long lens. The 55-200 is a good value used if you don't need that extra reach. All three lenses are good overall.