In general, the accuracy of a 2.5" gun isn't much different than that of a 4, 6 or 8" gun.
Ahh, but the devil is in the details.
A 2.5" gun can be harder to shoot at optimum accuracy than a longer tubed gun.
Two main things play heavily.
The first is balance. The more weight out in front of your hand, the steadier you are on target.
Only to a reasonable extent; once the gun becomes too heavy overall to hold comfortably for an extended amount of time, accuracy is obviously impaired.
The second is sight radius. Aiming is a confoundation of vectors, angles, degrees and varied focal distances.
The closer together the front and rear sights, the more point of impact deviation you get by moving left and right, up and down.
To ballpark it, I think I remember an example where a gun with a six inch radius (as may be found on a 2.5" gun) is aimed at 25 yards, and if the front sight is moved .01" off side, it causes an 18" or so impact deviation.
At the same distance and same sight movement, a 6" gun with 9.5" radius suffers only a 6" impact deviation.
To be honest, I know my numbers are off. I'm only ballparking it, and I don't have a calculator with me so I can't work out the geometry, but the fact remains, there is less error with a longer radius.
So, to actually address your question, a 2.5"-3" M19, or 66, or 64 or 65 or 10 or 13 or 547 etc etc is a fine gun. But, for learning on a revolver, most people have better luck with a 4 or 6" gun, especially if you plan on using magnum ammo as a routine.
Oh yeah, that brings up points three and four: with more weight forward there is less vertical muzzle flip in recoil, and with greater overall weight there is less felt recoil total; both of which add to a successful session at the range.
Get the gun you're looking at, as that is the one you fancy; and also consider getting a used or police traded-in 4, 5 or 6" M10, M13, M14, M15, M64, M65, M66 or in L-frame a M581, 586, 681 or 686.
And now that you're hooked, we need to talk about a K-frame .22LR revolver. The M18 is wonderful, as are the various M17s and M617s.
Have fun! -Kframe