I don't have one, but if I were to get one with a smaller hoop (18" I think) rather than the too large. I have read that it can be difficult to reach across a larger hoop.
I used to have a PVC floor frame, but it bothered my back. The lap hoop I have now is no longer made, but you might want to consider the Grace lap hoop also. With a lap hoop, both hands are free. The good ones -- such as mine and the Grace -- allow fast, easy adjustment of tilt and minimize obstruction to the underneath hand.
The major difference I see between a lap hoop and a floor hoop is that the floor hoop keeps the quilt off your lap. This is a big advantage if you are quilting during the summer without air conditioning.