Thanks for all the replies.
This morning I tried out both, shoot one then pick up the other. I found I much prefer the 305 grip. The recoil felt about the same with both, the 405 was slightly less. The main reason for my preference is I couldn't get a satisfactory purchase on the smaller of the two. One must have absolute confidence in their ability to handle their carry piece and I just didn't have it with the 405 while I did with the 305.
The "pinky under" feeling just does not feel secure to me, I could shoot with it okay once I got a good hold of it but that took a little longer on the draw than the 305. The fumbling feeling I had was not confidence inspring and the slight hesitation is getting off a shot could make a life or death difference.
While shooting one handed, my group at twenty feet was almost an inch larger with the 405. A two hand grip with both was dramatically better and especially with the 305.
Let me end with saying this-these laser grips really do work. I have never shot a 642 this good, and I've been trying for over two years! A couple of times, with the 305, I had two or three of the five holes touching. This is using both hands and concentrating on the red dot with the gun aligned about chin level. One time I shot from the hip and again was very pleased that all holes could easily be covered with a clay pigeon (approx. 3.5" diameter). Speaking of clay pigeons, on the draw from any fighting distance you just cannot miss!!
I was a bit skeptical about laser grips, but I am sure a believer now.