I've got 6 Bar-Sto Precision Match Barrels. When it comes to great pistol barrels it's kind 'a a toss up among: Bar-Sto, Kart, and Schuemann. Maybe Jarvis is in there, too.
Bar-Sto barrels are tight, alright! I have to slap the side of my slides to get a loaded round to fall out. Overall I believe these barrels to be stronger, tighter, and even the, 'drop-in' barrels are built to closer tolerences than any factory barrel. Most often it's the vertical sides around the chamber that need to be fitted. A few swipes with an oiled Eze-Lap hone will usually take care of this.
If you send the pistol to 29 Palms, Irv Stone will do a great job for you; but, there's nothing wrong with the drop-in barrels. They're, still, light years ahead of factory stock.
With the 357SIG you might want to consider a half inch barrel extension with, 'slit-ports' right behind the muzzle. Really smooths out recoil and aids greatly on repetitive fire. It's in the Bar-Sto catalog.
Here's a link for do-it-yourselfers,
http://www.knivesplus.com/EZELAP.HTML
And here's Bar-Sto,
http://www.barsto.com/