The variables here are the profile on the selector, i.e., the depth of the grooves and how "sharp" the edges are, the sharpness/roundness of the point of the selector detent, and the degree of preload on the selector spring, which controls how hard the detent is pushed against the selector.
Varying these three things will affect how your safety feels, how much resistance it has moving in and out of position, how much force it takes to change mode, and how positive the feel is.
A well broken in safety will have worn the sharp edges off the
selector, the point off the detent, and will have made the spring a
little more relaxed.
But in a new gun, if the hole in the grip is a little deeper, or the hole in the lower is a little off, it can affect those variables and make the same spring/detent/selector feel different when installed in a different receiver and/or pistol grip.