I have used Guterman and Mettler silk finish and I just started using Aurifil. My machine seems to love the Aurifil. It even sounds different when I use it. I wouldn't get rid of the thread that I have to use Aurifil but as I run out I will replace with it. I will say that I can get a scant 1/4" with the Aurifil without much effort. However, when I'm quilting (not piecing) I go with the brand that has the color that I am looking for.
Each person has to go with what their budget and desires dictate. It is nice to try all different brands of supplies until you find what works for you. That is part of the fun.