My personal experience is that I generally find the Boundless fabrics a little thinner and stretchier. Even though I have a Bluprint membership, so free shipping and some good deals, I don't buy them. I bought several 5 inch packs of their Fractals line, thinking the patterns were so great, but once I received the small pieces, I didn't turn around and order yardage. I wish Kona would pick up Fractals because I adore the designs! I have a kit that Bluprint gave me for "free" with my membership and I think that fabric is stretchier than I'm accustomed to, making it semi-difficult to piece the rather complicated design. I am not a fabric or thread snob. BTW, it's a huge quilt, very intricate and is still turning out pretty overall, just a little harder to work with when piecing things on the bias.
In general, I like the Kona cottons, followed maybe by Michael Miller. I steer clear of Moda, to be honest because I think it's thin. I find the Grunge line especially so. I'm surprised when anyone says they prefer Moda to Kaufman and think they must be mixing up their fabrics or something.