Your preferred thread for machine embroidery

[Jane_moon]

Even if might sound obvious, there are many kinds and brands available. But I'm talking about the material mostly: cotton, silk and wool. So I would like to ask, which thread brand(s) and materials do you prefer? And why? 
Or it purely depends on a project? 

As for me, I've tried using Sulky brand in my embroidery machine but it keeps breaking (even with lower tension + speed). And now I'm curious about Madeira thread, but I have no local quilt shops that stock it so I will have to order online. 

So as I'm waiting, I would like to hear other's experiences, in case there are any. What works for you?

[Jane_moon]