Without knowing what "better" means to you the answer could be yes, no or maybe.
Yes same frame and assembly they will interchange
No. You can get a Sig P229 that will fire .357 Sig, but that is not the same as .357 magnum.
Yes, as long as it is made specifically for the P229/P228.
The P229 pistol is made in 3 different calibers- one of which is the 9mm Parabellum, also known as 9mm Luger.
The Sig P228 and 9mm P229 both use the same frame and frame assembly. The difference is that the P229 has a machined stainless steel slide, while the P228 has a stamped slide with a breech face block pinned in place. The P229 is stronger than the P228, but the P228 is a little lighter. I personally prefer the P229. The P229's tougher frame makes it better than the P228 for stronger rounds like the .40 or .357 SIG (I don't think the 228 even comes in those calibers).Yes it does amd the p228 is easyer to mass produce.
No published sn data.
You posted the question under computer terminology, but I'm going to assume by Sig P228, you're referring to the handgun. The P228 was discontinued was because the P229 was a more popular seller, and after the P229 became available in 9mm, there was to particular reason to continue selling the P228. Additionally, the P229 frame is milled from steel, making it a little sturdier than the P228, which was a stamped frame, which is probably at least part of the reason the P229 was more popular.
ENTIRELY too many agencies to list here- but if you scroll down to the link that says SIG P229, it will take you to the page of Wikipedia that shows the major user.
Sig Sauer P229
One can purchase a sig p229 at almost any gun shop location such as NRA or hunting shop. Be sure to bring proper identification papers, permits, and payment.
Look on the frame.
SiG P229 in 357
There are not many shortcomings for the Sig Sauer p229. It is a pistol that has been repeatedly tested by the United States government and is carried by many members of the United States armed forces and federal agencies.
About 50 meters.
Sig Sauer P229
It was proofed in 2006
You will have to call SIG to find out
Impossible to answer withou a DETAILED description of ALL markings.
It was proofed in 06
Sig Sauer P229, .357 Sig
P229 Sig Sauer in .357