I prefer a lap hoop. It is not hard on the back, it is easy to adjust to suit your preferred quilting direction, it is stable, and it leaves both hands free. My favorite lap hoop swivels on a wooden ball but is no longer sold. The closest thing to it is the Grace lap hoop:
http://www.graceframe.com/site/hoops . There are some reviews of it on Amazon:
http://www.amazon.com/Grace-Company-...dp/B003AJZVIY/
Advantages of a lap hoop over a floor hoop is that the lap hoop is easier to move around, more compact for storage, and (for me, anyway) easier on the back.
I hand quilted my first quilt on a Q-snap floor frame, but it is definitely not good for someone with a bad back. Had to give mine away. Before that, I started out with a regular round quilting hoop (no stand), but found it awkward to always have to balance the hoop in order to quilt with one hand underneath and one hand on top. I also tried quilting without a hoop. My stitches were much less even, especially on the underneath side.