The extra 1" of barrel length does indeed make for an entirely different gun. That extra 1" gives it a longer sight radius, a longer ejection rod for easier extraction and loading, and better balance. It also makes a "pocket gun" into a "holster gun."
After trying a variety of 2" J frames, 3" J frames, 2" K frames, 2.5" K frames, 3" K frames, 4" K frames, 4" N frames, and 5" N frames, I have settled on 2" J frames for "pocket carry"/deep concealment, 2" K frames (and sometimes 4" "pencil barreled" K frames) for "belt carry"/IWB, and 4"/5" N frames for "field carry."
Preferences obviously vary but I have found that:
-having a longer barrel on a J frame negates the advantages of the smaller frame.
-2" K frames and 4" "pencil barreled" K frames carry more easily, draw more quickly, and point more naturally than either smaller guns or "heavy barreled"/"full lug" guns.
-the N frame is the ideal platform for any cartridge bigger than .38 Special (of course, it is also a pretty darn good platform for .38 Special too).