I have to hang my head in shame . . . and admit I'll use whatever is handy. I have Mettler, a bit of Gutermann (came with machine), and a lot of Coats & Clark. My machines don't seem to care what I use, thank goodness. As for needles, it's usually a 14, for quilts. If I'm sewing clothing, I'm just as likely to use a size 11 (or 9, if the fabric is thinner).