One thing I'm a bit hung up on: this is a 2.5" barrel SP101?
If it REALLY is, grab it if it's factory, 'cuz that's one hell of a rare combo.
More likely, you're not measuring it right, you need to measure the part of the barrel that's screwed into the frame too. In other words, it's probably the 3" model. Which is good, in my opinion: the SP in 2" is still just a bit big for front-pocket carry (esp. with a cockable hammer) so if you're going to need to holster it anyhow, might as well go 3" and get a speed boost on the ammo. The 3" variant will conceal in an IWB, basic belt rig, shoulder rig or fanny pack. The only time a 2" barrel will really help is with an ankle rig or pocket carry and I'm not a fan of either for this gun...your milage (not to mention wardrobe) may vary though.
What I mean by speed boost: if you're new to handguns, full-house 357s in this size gun will be a handful, and they'll be noisy as hell indoors. So you might end up loading 38+P for defense. There are now some quite good 38+P loads tuned to work out of 2" barrels (barely) - the extra 50 to 75fps from another inch of tube will help put those "over the top" into guaranteed decent performance.
As you step up the power, one option in 357 loads is the 158s at relatively mild speeds, like the 158 Speer Gold Dots set up for 1,250ish out of a 4' barrel. We know these need around 1,100 - 1,150 to expand properly, so that load from a 2" is...iffy. From a 3"? Oughta do just fine, without the "crash and fireball" of the hot 125s at 1,400 - 1,500 fps.
So at these two power levels, I think there's a significant gain in a 3" over a 2" barrel.