The 642 is a great carry weapon. If wanting all steel construction and .357 magnum capability, I'd go with a 640 although I think the 642 is the better bang for the buck and a much better choice if wanting to pocket carry.

The 649 has never made much sense to me. It's neither here nor there and ultimately a bad compromise since single action is of little practical benefit on a gun whose purpose is close-quarter personal defense.

I owned a Ruger SP101 years ago and never warmed up to it. Too heavy and bulky for only 5 rounds and I found the trigger difficult to manage in rapid fire. I promptly sold it and bought a 640 which I eventually traded in for a second 642.