It's more a matter of personal preference than which is "better".
For generations, before stainless steel was used to make firearms, nickle plating was preferred over bluing for it's resistance to humidity, corrosive priming and black powder residue, and easy maintenance.
With the advent of stainless steel revolvers and pistols, carefree and low maintenance are it's outstanding virtues. There is no "finish" to wear off or corrode. If scuffed or scratched, some carefull rubbing with the proper abrasive medium is enough to restore it's appearance.
Modern nickle finishes are quite durable, but still subject to impact damage, scratches, and scuffing. Relatively little needs be done to keep it looking pretty.
Of the two, for extended outdoor use in inclement weather, or for minimum maintenance requirements, stainless gets the nod of approval.