I can not say for sure because I have only used the RS 49-425. The only other PIR I am familure with is the Regent MS20. Both seem to work well based on information here. I picked the RS PIR due to size. "Smaller is better" at least I keep telling myself that. . I think the Regent may be a little more stable in the elements of the outdoors. And the Regent may have a longer field of fiew than the RS PIR. Other than that I can't tell you much more, but maybe some who has used both can.