My P229 shoots very well Ive carried it for 7 years!
Is there a good reason to buy the 357sig barrel?
Ive never fired this round!
Whats the Pros an Cons

I'm intrigued with it, but I don't know why. It's a really fast 9 millimeter, and I'm not really sure in a defensive situation that the bullets made for lower velocities would hold up.  It appears to be very flatshooting though, and I know that it has a hell of a muzzle blast.

A 10mm is next on my list, but maybe after that, a 357SIG

I have a SIG PRO in .357 SIG. It's a lot of fun, but for me it's more of a novelty. The rounds are expensive, but at the same time they're loud and fast!

Quoted: Is there a good reason to buy the 357sig barrel?

Because you can another caliber for under $150. Whether or not this round will be largely accepted is still yet to be seen but the use by several larger Federal, State, and local Law Enforcement agencies makes it more likely that this round will get a lot more exposure. I think that it is a fun round to shoot although as mentioned it is expensive. I shoot mostly .40 in my P229 but on occassion drop in the .357 Sig barrel and let some fly downrange. It is especially more fun when you are shooting with someone who hasn't done much shooting and you let them shoot the .357 Sig. Not as much fun as letting someone shoot a .357 magnum revolver with .38 Special semi-wadcutters and then loading up some full-power combat level .357 magnum rounds, but still fun.

Personnally, I'd opt for a 9mm conversion barrel.  You get to practice more with the same $, and saves some wear and tear on the pistol.  Nothing wrong with the .357 other than its more expensive, and it causes more wear & tear on your pistol & you.  Besides, you already have the .40 for that

Sig makes the claim that you can not go to the 9mm with the .40/.357 229.  They dont list having a barrel for the 229 in 9mm.  

I know Bar-sto also sells barrels which they say are for 229 in 9mm, but that goes against what sig will tell you when you call (I did).

Thats another thing I dont get ? Why make a P229 in 9mm? You can have the P228/M11!!
I think I will stick with the 40cal barrel.

Stainless slides and rail options I guess.  I personally favor the 228.

i bought a 357 sig barrel  for my sigpro like was said a novelty more then anything a 9mm on steroids necked case no feed issues reliable good for personal defense i think now that i have my CPL i carry my sig pro with the 357 barrel !!

Quoted: ...Is there a good reason to buy the 357sig barrel?...

Personally, I can’t think of any!

I guess there might be some merit to it if you’re a state trooper and anticipate having to shoot through a car windshield or door panel.

Also, 357 Sig recoil is a bit tamer than a .40, which might be an issue in a lightweight semi.  But a P229 is both pretty hefty and has a good sized, comfortable grip, making even the .40’s recoil very mild.

If you’re anticipating TEOTWAWKI, having an extra barrel in a different caliber would give you extra options during an ammo shortage – except that .357 Sig is almost certainly going to be harder to find than .40.  OTOH, in this context a 9MM barrel makes a certain amount of sense.

Getting a 9MM barrel so you can shoot cheaper ammo sounds like a worthwhile idea - assuming you do a lot of shooting – but I’d think the point of aim would change.

I can't say for sure on the Sig, but I had great results with Barsto 9mm conversion barrel for my Glock 23 (was .40).  The POI/aim was not really affected in my case.