I have a longarm....and do most of my own on it. But, I do not do dense..I prefer my machine quilting to be either mimicking handquilting or just panto type...I also enjoy handquilting.... That being said, I think the dense quilting is stiff not only because of the brand/ type of batting, but also because for every stitch there are two threads locking, not just one thread running.......
I have two whole cloth bed quilts(acquired) that are heavily hand quilted and are soft.....and I think if they were machine quilted with the same patterns those quilts would be stiffer than they are....JMHO