I think machine quilting and hand quilting are two different things. Various kinds of thread can work well for machine quilting. For hand quilting, my preference is thread made specifically for hand quilting. Since it is coated and stiffer, it threads much easier and glides through the fabric easier with much less tangling and knotting. Hand quilting thread is made in a specific way for a reason. In your situation, I would finish quilting the quilt with the thread you have been using and see how it holds up. Then on the next project, I would try hand quilting thread (which is always cotton) and compare to see what quilts best for you.