The Bernina has a proprietary bobbin that isn't a standard size, but it is extra large. No problems with the winding, it is simple easy and fast and doesn't require rethreading the machine (if you use a different thread).
I mentioned this model was not well received, it also comes with an embroidery module that I don't have. Personally, from watching my friends with embroidery machines, I'd want the convenience of prewound bobbins. But we get used to what we must do, so while it makes me cranky to wind 6 bobbins at a time, I've certainly done that too.
I have a bunch (but not all) of subunits to sew together today, I think I'll leave the So Fine in and try piecing with it. It will be a good test without being a huge time or cost commitment.