I only use 50 wt. for piecing, but sometimes use 40 or 30(heavier) for quilting. It's all based on preference and the amount of quilting you prefer in your quilts. If you use heavier than 50 wt. in piecing you will have to change your needle position to get the scant 1/4". If you do a LOT of quilting or thread painting then 50 or even lighter 60 wt. may be more what you're looking for. Honestly, I've got a thread stash going and enjoy the freedom of my different weights, colors and variety to choose from!