I own both, and find the Kiwa to be better for MW. The nulls seem
sharper and the ability to tilt the loop (I think it's called azimuth?)
helps in nulling skywaves. The QX-PRO is smaller, thus easier to find a
spot for. The Kiwa doesn't receive LW, so of course the QX-PRO has the
LW advantage. Both are great antennas and you can't go wrong with
either one.

If memory serves, neither are manufactured any more.