I am as environmentally friendly as anyone... but show me why I should use organic thread.
I primarily use Mettler's Silky 50/2 for piecing, I use 100% cotton 40/3 thread of different brands for most quilting. I like the thickness it gives my quilting lines. I do have some of that Egyptian 100% cotton thread, but you know, it doesn't make much difference in the machine.
For 50/2 I use a size 75 needle, for 40/3 I use a 90.
Having the strongest thread is not necessarily the best option. Too strong a thread, it will eventually cut your quilt fabric into small pieces. I did use a polyester thread (Sewfine)on the back of my latest quilt, but it's because my backing fabric is fairly heavy compared to normal quilting 100% cotton fabric. I suspect that quilt will out last me, and my daughter who gets it and she is only 12.
tim in san jose