Depends on how well you're willing to maintain it to some degree.
Blued is blued. In this age of hardening treatments and hostile environment finishes, I sometimes wonder if some folks have forgotten how to care for simple blued steel. I remember seeing guys take their blues steel revolvers out of the wet leather holsters at the end of a shift and wipe them down with a towel before sitting them on a shelf in their locker so they wouldn't rust and the holsters would be dry for their next shift.
Nickel is nice, but be careful what solvents you use for cleaning. Also, depending what sort of deodorant you use, I've seen minor discoloration & almost surface etching occur if it sifted down through clothing onto the surface of the metal (like the bell of the frame or beside the hammer). It can wear, become damaged and come off, too. I've had the nickel react to different leather, too.
I happen to like nickel, and wish I'd kept an older model nickel 3" HB 36, and I've sometimes thought of picking up one of the new M40's in nickel.
Stainless is for those of us who are somewhat lazier (or busier, perhaps), or who carry their weapons under more arduous and unfriendly environmental conditions. They can still oxidize, and require some attention, of course ... but they're a bit hardier under most conditions.
I believe S&W uses a passivated stainless steel finish for their stainless guns. I'm not sure which process they use. Passivation of stainless steel is sometimes described as the treatment of stainless steel in nitric acid or other materials to make it less prone to rusting. Another description is the removal of exogenous materials and iron from the surface, thereby "chromium enriching" the surface. This is followed by oxidation of the chromium to form a corrosion resistant layer of chrome oxide on the surface.
I've never understood the folks who do their own kitchen-table polish jobs on stainless revolvers or pistols (or even magazines), since it can damage the passivated surface.
It will still scratch, and I've always felt that brush stainless finish guns showed minor "swirl" scratches more easily than blued or nickel guns.
Personally, I think a J-frame collection really needs a nickel model to complete it (which is an excuse I may use to justify my purchase of another one someday

).
Luck to you in your decision.