I considered both and went with the SP-101 and I absolutely love it. Admittedly it has a heavy trigger pull, which will take some work to lighten up. Otherwise it is just about perfect. I love the high visibility sights and the solid feel of it. Shoots great and the 8 round cylinder is not aluminum as the M617, but heavy stainless steel and should last several life times.

Also no Internal Lock to fuss with and since I own other SP-101s it is a great practice gun. The balance and feel of the gun is excellent.

My only regret is that two were available at the great price of $510, and I only picked up one.