I can think of having learned of some shooting incidents where rounds that often seemed to penetrate beyond the "acceptable" distance in gel testing, turned out to perform differently in an actual shooting. In one case I remember where 1 common major maker 180gr .40 JHP that traveled more than 18" in a 4LD test (without expanding), when used in a later shooting was deflected by bones in an arm (remaining trapped in should capsule after being deflected in lower arm), and the other round remained trapped in the pelvic area.
One of our guys came upon a murder victim who had been shot in the COM with a .45 ball round, which was deflected off the anterior ("front") of a shoulder blade, and then traveled downward into the lower torso, remaining inside the body.
Since our choices for duty/off-duty ammunition was subject to concerns about possible perforation of the intended threat, to minimize potential risk to anyone beyond the intended threat, it became common for policy to limit choices to good quality, factory JHP loads for duty use (albeit special purpose ammunition could be approved, subject to review and approval), and it was generally recommended for off-duty carry, as well (if it wasn't a normal "duty" caliber, for which we would usually be able to provide off-duty ammunition).
However, as was pointed out in the FBI paper at the end of the 80's, each shooting incident could be unique, due to the huge variability of conditions, situations and circumstances. It was also commented that both lab testing and street results had their value, and if someone wanted to "prove" some particular result, it was always possible to select (cherry pick) shooting incidents in which the "results" might be shown to vindicate one preference ... as well as a contrary preference.
It's not unusual for shooting enthusiasts on public gun forums to often extol the "virtue" of penetration over expansion. Luckily for all of us, improvements in modern ammunition has given all of us some better options and possible choices for choosing both "duty" and personal defense ammunition.
I'm certainly nobody's "expert", by any means, though.
Personally, I'll almost always opt for the potential of expansion, or at least significant deformation, over sheer penetrative potential. Expansion can create more possibility of the type of wounding capability that might better cause injury to the critical tissues, structures and organs which might result in the "threat" to lose the ability for further volitional actions (meaning the violent actions originally presenting an imminent risk of serious bodily injury or death to the defender/victim).
Once upon a time I believed in carrying a .44 Magnum revolver off-duty (it was approved for both optional duty and off-duty usage in revolver days). I originally carried the hot 180gr .44's, although I could only find 240gr JHP's at times, and eventually started carrying W-W 210gr STHP's, which were sometimes considered more of a mid-range load (so to speak). As time passed I became increasingly concerned about the risk of threat perforation (over-penetration, if you will), and finished my days of carrying a .44 loaded with the less potent .44 Spl STHP off-duty. At that point, I figured it was simpler to just carry my Commander. Lighter and less bulky for both IWB and OWB, anyway.
If I were a handgun hunter (I'm not), I'd value heavy bullet weights and bullets designed for deep penetration of game animal skin and anatomy. For self defense against humans (or even feral/dangerous dogs or mountain lions), I prefer to rely upon less powerful loads, with expanding bullet designs.
All of us, whether LE or private citizen, may someday find ourselves having to face the consequences of our choices in ammunition, and while misses of an intended threat are arguably a much more common risk to consider and keep in mind, I still think it's prudent to keep the risks that may occur regarding potential "threat perforation" in mind as well.
We can't ever "call bullets back", after all.
Besides, after a career working in LE, which involved being in situations in and around motor vehicles, and other common hard barrier materials, I'm not someone who stays awake at night worrying about whether my retirement CCW ammunition can "defeat" layers of wood, sheet metal or other hard barriers.