Aurifil is finer than Iris Ultra even though they say it is the same weight, but it is also weaker (guess it's because it is 2-ply vs. 3-ply). I've used Aurifil for FMQ, but I don't use it for piecing. Just my preference. I agree that Gutterman is very linty. I tried it once and will not use it again. I do like Mettler silk finish cotton