I just love it when someone asks for the "best" of something and does not define the parameters.
If we mean quality, well, I have quite a few that are tied in that regard, made by the same company, Ruger.
If we go by what gets the most carry time, well that would be Ruger SP101. So good, I own several, and during a certain period of my life, 2002-2007, I carried two concealed on my own time, and one as a back-up at work, making the SP101 my true "always" gun during that time. I still use SP101s some of the time, just not 24/7 anymore.
If we mean that would be best for the widest range of circumstances, well, that would be Ruger GP100.
Best compromise of size, weight, and concealability? That could arguably be my 4" Speed Six, almost as easy to conceal as an SP101, but with a longer sight radius, and able to throw magnums at a higher velocity than a snubby. I never settled on a truly good grip for this sixgun, before I started toting my P229 duty pistols on my own time, concealed, relegating my larger sixguns to spending most of their time in the safe.
Best deep concealment/pocket/ankle revolver? I have a J-frame S&W Performance Center M460, which was built on a J-frame, and closest to today's Model 642. (Not kidding; S&W has re-used that model name for for their X-frame .460 S&W.) Once the SP101s came along, though, this little gem was relegated to "occasional" status; my usual minimum gun, to this day, is an SP101.
One sixgun I really miss, is the S&W 4" Model 19 I owned briefly in the mid-1990's. One of the last blued K-frames with the forged trigger and hammer, and of course, pre-keyhole, that was a smooth, accurate sixgun. I sold it, along with other guns, to raise funding for a now-regretted reason. I am still seeking its twin, preferably one fired very little, and lovingly maintained. I even have a pair of BluMagnum grips awaiting such a purchase. I would have to handle it before buying, to make sure. This may be my true best, if I ever find it. I realized, too late, just how right Bill Jordan was, and underestimated the difficulty of finding another one if I let mine go. My "Holy Grail" sixgun is in my future, I hope.