Weeelllllll coyotejoe, I carried a gun for 20 years as a police officer. Weapons instructer 19 years for dept. ran SWAT team for 5 years of the 20, and Tactical K-9 for 13. While SOME cops just carry because it is necessary, many are VERY knowledgeable, in function and use. No all are not ballistic experts, but they have researchers, that using DEPENDABLE and ACCURATE data, from a RELIABLE SOURCE, from ACTUAL shoot situations involving officers, to inform them on best caliber, load ect. However, many dept. heads ignore the data, to satiisfy their own beliefs, real or imagined, as do some citiziens.
Your ill concieved notion that the 9mm got a bad name with cops because of the belief "that heavier must be better" which caused them to go with the 147 grainer is completely the opposite of true. The 147 grainer was CONCIEVED trying to improve a bad stopping record that the 9mm earned on it's own, and it (the 147 grainer) does not make it into a semi auto 38 special. It makes it into a 9mm shooting a slower 147 grain bullet.
What you mistake for load preference is acutually about ENERGY DISPLACEMENT. The 357Sig may or may not "RUN" a 125 grainer faster than the same bullet weight in 357 mag, regardless of barrel length however, the "ENERGY DISPLACEMENT" will not be the same, BECAUSE OF "CALIBER" and "BULLET CONFIGURATION" which DICTATES "ENERGY DISPLACEMENT".
I started watching FBI stats on one shot stops back in the early 70s when the 9mm wasn't yet popular, and the revolver was still king. As the 9mm and others began to enter into the fray more, I noticed the stats did not change on caliber, or bullet weight and configuration. Everyone else noticed also, and an effort to pump up the 9mm poor record, in order to salvage all those 9mms caused the conception of the 147 grainer. The Illinois highway patrol and others had invested much in this new police caliber, and where not pleased with it's performance reports coming from the field. Also working in CID and Narcotics I had the opportunity, or mis-fortune however you prefer to look at it, to see many gun shot wounds with numerous caliburs and gauges. I once worked three fatal shootings in one 14 hour period.
So it really doesn't matter whether anyone "believes" anything. It only matters whether the stats are accurate or not. Some people will stand soaking wet in driving rain, and swear it's dry, if it doesn't fit their own imagined idea of how something should be.
I have personal experience of the difference in "reality and tv", but then again I have personal experience of the difference in what something really is, and what someone whom has no experience thinks it is, because of what they have read, or thought they knew. They are seldom the same.
The obvious fact remains regardless of denial by some, is that the 125 grain hollow point out of the 357 magnum HAS the best one shot STOPPING record in L.E. forcement and has for years. It is obviously the best KNOWN compromise for weight, penatration, and hopefully expansion along with ENERGY DISPLACEMENT. Better than the 44mag. ,45acp, 38 special and the 9mm. Also fact is ANY caliber DEPENDANT on expansion is set up to fail, as something as simple as clothing can plug the hollowpoint there-by voiding the hydrolic design of the bullet. These facts did not come out of a gun rag selling bullets and guns, or my head. They came from actual stats.