I watched a Youtube video that included some explanation of the Brother 90 weight embroidery thread. Apparently 90 weight does not always mean the same thing; that is, 90 weight is not necessarily equivalent across all brands of thread. Here is a link to the Youtube video that explains it better than I can:
https://www.youtube.com/watch?v=epHN...WY4exet0vFO4MP
What I have gleaned recently is that the Brother 90 weight thread is manufactured in a specific way to work exactly as required in Brother embroidery machines. If it works well in your Bernina, I would stick with this brand of thread. If I am remembering correctly, the Brother thread is manufactured in Japan to very specific specs.