I have a 4 needle MB4 and I always wind my own bobbins.

I have a 15 needle machine, and if I want my btm thread to match, I use the winder on the embroidery machine . On other things I use the prewound white bobbins. I buy them by the box of 144. I save some of the empty bobbins to wind my bobbins for the FSL ect.

I have a 6 needle and I normally use the prewounds but for FSL I wind my own and use the Sidewinder. I have a single needle machine also but it doesn't do as good a job as the Sidewinder.I love FSL and do a lot of it also.
Hope this helps.

i am sure others will help. I don't know.

I have a 4-needle and use pre-wound for white and black, but for FSL I wind the bobbins on the machine. That works well. So no horror stories I'm afraid.

Ha! Only ONE needle (unless it breaks...).
But we always use matched self-wound bobbins.
And, as we've recently found out, if you keep a little pressure on the winding-mechanism (Bernina Artista 185), you can get much denser packing and there is not much advantage of using any pre-wound bobbind at all.

I always wind my own bobbins (4 needle mach).

I, too, wind my own bobbins for FSL (4-needle machine). The machine winds far better than my household machine and gives excellent results when embroidering with those.