I have crimson trace on my 638. I keep this one in my car. I have JP electronic sights on my 617 and 686. These I shoot at the range. I actually have laser sights on all my other guns, 1911's and XDM's. I have to stop and think for a minute. I have crimson trace on my Ruger 5 shot revolver. This one I carry with me.
I have Crimson Trace on all my main carry handguns (4) they are great. Try them on a snub nosed at 50 and 100yd you will be surprised. One still has the regular sights available when it is too bright for lasers. Also good for dry fire.
Gene