Slight increase in MV from the longer barrel. Longer sight radius makes aiming a bit easier, increasing accuracy potential.
On the other hand, almost totally eliminates the possibility of pocket carry.
Have had them both. Stuck with the 2". Carries better, in my opinion.
With a 3" you also get a full-length ejector rod, so dumping brass for a quick reload is easier. Sometimes with a 2" you have to shake or pull the brass out because of the shorter ejector not able to push the brass all the way free.
If that chart is accurate, then the best increases in muzzle energy are to be found by going from 2" to 3" or from 3" to 4". IMO, this makes it something to consider.
More power, better practical accuracy, less recoil, full-length ejector. And the trade-off is 1" overall length (or 1.125" when compared to a 1.875" snubby) and an ounce or two in weight.
I find a big difference in the ease-to-hit department, and no diff in the ease-to-conceal one. Concealing the grips is the hard part for me. YMMV, but for me, it is the 3 incher all the way.
I have a 2 1/2" S&W 66 and a 3" S&W 65. For me the 65 seems to balance better than the 66. Granted they are 357 Magnums but I use 38 Special +P ammo in them most of the time.
The 3" Ruger SP101 seems to point better than the shorter barrrell version. Assume that would hold true for other makes and models. Its my favorite barrell length for all-around carry and use.
Like some others, I don't think that the 1" difference makes much difference in terms of ballistic advantages/disadvantages, concealability or shooting/handling performance. That said, I prefer the three inch barrel length a little more than the two inch length because it offers slightly better ballistics, slightly better (subjectively speaking) balance and handling (pointing) shooting performance, slightly less recoil and muzzle blast-and at no real loss in concealment benefit (though Yankee Doodle's caveat regarding pocket carry is duly noted, depending on the size of the pocket).
In a short barrel(snub) type wheelgun, a 3" barrel makes more sense. You get slightly better ballistics, a longer ejection rod & better marksmanship.
A 2-2.5" revolver is good for some applications; ankle-pocket carry, 2nd gun, etc but most gunners like 3" barrel snubs.
Author & tactics instructor; Massad Ayoob wrote that the long ejector rod design & improved ballistics made the 3" barrel revolver a better pick for duty-defense.
I have both a 2-1/2" 66ND and a 3" 66-2. Not enough difference in accuracy to matter much.
Big difference in the ejection of shell casings. The 3" has a Full Length Ejector Rod.
When carrying concealed I find the 2-1/2"and 3" are almost the same. Note: the 3" is about on the outside limit on concealed carry barrel length for me. I do carry a 4" some, however I need to pick what I am wearing more carefully.
The shorter 2" barrel on a K Frame Snub like a Model 10, 15, 64 or 65 is definently easier to conceal than a 3" K Frame. That 1" less barrel makes accessing your bill fold easier in your right back pocket.
My calculations on velocity with 135 Speer Bullets in Quick Load:
Here are two loads with the same bullet, primer, brass and powder charge that I chronographed myself: the difference was 50 fps velocity gain for the 3" barreled gun.
S&W M-637 with a 1-7/8" barrel, 125 gr Remington JHP = 829 fps.
S&W M-36 with a 3" barrel, 125 gr Remington JHP = 879 fps.
For concealed carry, I find no real difference between them from a concealability standpoint. I use a belt holster in the "FBI" position, ie. 4 o'clock on the strong hand side with a slight forward cant.