I do think that getting a few opinions from "dudes on the internet" is better than nothing. I do give more credit towards people who have wide access to reports on shootings: cops.
I've read two of Massad Ayoob's books, and here is one that talks about defensive ammo & calibers:
Amazon.com: The Gun Digest Book of Combat Handgunnery: Massad Ayoob: Books
Both are excellent rounds. According to that author's findings, the 357 SIG doesn't blaze through multiple people: he stated that the rounds usually are found a few feet behind the person.
The 357 SIG was already super expensive in the "old days" and now ammo prices are just getting ridiculous; so I wouldn't buy into it unless you're rich.