Welcome to the board! As you've already gathered, it's a matter of personal preference (and perhaps budget, lol).
I'm one of those who match thread to fabric, so it's cotton for me; the thinner the better for piecing and 30-50wt for quilting, depending on the look I want. I do quilt occasionally in polyester, rayon and metallic, but usually it's Presencia or Aurifil for piecing and Superior King Tut for quilting.