I suppose that depends on what you consider "much better". I chronographed Federal 158 grain .357 Hydrashoks out of both my 2 1/4" and 3" SP101s, the results were not that different.
You tested Federal. That was a mistake and a half. Carrying Federal is an even bigger mistake. Federal wimps out on powder charges, esp. on wheelguns. This is a well-known issue.
Try some REAL ammo from Cor-Bon, or better yet Buffalo Bore or Doubletap Ammo. You'll get a much different result.
Here's some published Buffalo Bore data:
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1. 3 inch S&W J frame
a. Item 19A/20-180gr. Hard cast LFN = 1302 fps
b. Item 19B/20-170gr. JHC (jacketed hollow cavity) = 1299 fps
c. Item 19C/20-158gr. Jacketed Hollow Point = 1398 fps
d. Item 19D/20-125gr. Jacketed Hollow Point = 1476 fps
2. 4 inch S&W L frame Mt. Gun
a. Item 19A/20-180gr. Hard cast LFN = 1375 fps
b. Item 19B/20-170gr JHC = 1411 fps
c. Item 19C/20-158gr. Jacketed Hollow Point = 1485 fps
d. Item 19D/20-125gr. Jacketed Hollow Point = 1603 fps
3. 5 inch S&W model 27
a. Item 19A/20-180gr. Hard Cast =1398 fps
b. Item 19B/20-170gr. JHC = 1380 fps
c. Item 19C/20-158gr. Jacketed Hollow Point = 1457 fps
d. Item 19D/20-125gr. Jacketed Hollow Point = 1543 fps
4. 6 inch Ruger GP 100
a. Item 19D/20-125gr. Jacketed Hollow Point = 1707 fps
5. 18.5 inch Marlin 1894
a. Item 19A/20-180gr. Hard Cast = 1851 fps
b. Item 19B/20-170gr. JHC = 1860 fps
c. Item 19C/20-158gr. Jacketed Hollow Point = 2153 fps---- Can you believe this?!!!
d. Item 19D/20-125gr. Jacketed Hollow Point = 2298 fps---- Or this?!!!
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Note that the vintage S&W 5" barrel is shooting abnormally "slow" by the standards of both newer S&W barrels and Ruger barrels.
Pay particular attention to the difference between the 3" and 4" 125gr numbers - over 125fps difference. That's huge. And the loss down to 2" is worse.