RAD II hands down. Have one on my Beretta 682 and love it. I also have a Gracoil w/LOP Recoil system on a Browning BT99. It works fine but its not the quality of the RAD. IMO Rad has easier adjustments. Easliy removes for cleaning and oiling. Gracoil is slightly more difficult on both.
The RAD removes very easily from the stock and is easy to return to your preset LOP and cant adjustment. It does require the unit be removed to set tension. This is the design that betters the Gracoil. IMHO
You will find the gracoil spreads the recoil out over a longer period than a RAD or RAD II. Take a Gracoil and a RAD and compress them at a tight setting. The Gracoil travels twice the distance of the RAD before it bottoms out.
I have 2 RADII's and 2 Gracoils on guns I regularly shoot, and I have the RADIIs set next to max to keep them from compressing when I mount the gun. Not so with the gracoil.