The age old question, which of these bullet weights to pick for 9mm defensive ammunition? Proponents of both abound and they all have valid arguments. Heavier bullets tend to penetrate better due to the retained velocity they carry due to mass. Lighter bullets, especially when loaded to +p pressures, give you more slide energy and velocity to cycle your semi-auto, which, in theory, can lead to greater reliability, especially if you've gotten a less than amazing grip on the gun. Heavier bullets are subsonic, and therefore tend to be quieter, especially when suppressed. Each of those bullet weights has its very strong proponents.
That said, when it comes to terminal ballistics, most of the time there isn't any real difference, especially when it comes to Federal HST rounds. When I say "real difference," I'm talking about expansion differences between 0.60" and 0.66". The only place that makes a difference is in a lab where you have somebody taking precise measurements. And when it comes to penetration, if you look at Lucky Gunner's ballistics tests, the lowest penetration they recorded was 15.2" for 147gr HST, and the highest penetration they recorded was 19.2" for the 147gr +p HST. The 124gr stuff came in near the middle, with the regular pressure and +p pressure rounds penetrating at 18.3". These numbers truly fall into the "semantics" category, because these rounds perform quite well.
So with that out of the way, it is obvious to me that terminal ballistics isn't the decider in this issue. There are only two other factors that I really care about.
Firstly would be if you're running a suppressor/silencer/gun muffler. If that is the case, you'll want a subsonic bullet to capitalize on the sound reduction. While the 124gr loadings are nominally subsonic depending on altitude, the 147gr loadings are definitely subsonic. And if I want less sound, I want less powder pushing the bullet, as more powder means more gas which means more sound. That means I'm probably going to stay away from a higher pressure loading, so standard pressure 147gr wins this argument hands down.
The other factor would be accuracy. Now every gun is different, but I've noted a very interesting trend with generation 5 Glocks. If you're not running one of those, this won't apply to you, but it has held true in my Glock 19, my Glock 17, and my Glock 45, all 3 of them being Gen 5 guns. The 124gr bullets tend to give half the group size as the 147s in all three guns. In my Glock 45 the difference was notable even at 15 and 25 yards, but where I saw it play out the worst was at 100 yards. The 124gr load gave me a 6" and 9" group at 100. (This was sandbagged/rested, but not machine rest.) 147s gave me a 15-18" group. Now neither of these groups is horrid, but I know which one I would pick, and in case you're curious, I'm converting over to 124s in all of my Gen 5 guns. The only gun in my house that's going to keep the 147s is the one with the can on it.
So what about you? Which should you pick? Well in this market, whichever is available is probably a big deciding factor. In the land of the blind, the one eyed man is king. So whatever is decent fodder out there, pick it up. But secondly, since we know that HSTs work, do we really care? For most of us, it doesn't really matter. And if you are picky, do an accuracy test, see if one works better for you than the other. Whichever you shoot most accurately would definitely be my pick, were I you.
And if you're having difficulty with your accuracy, perhaps this video will help.
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On a completely different topic, here are some items that I recommend. Note that as an Amazon Affiliate I get a small commission on qualified purchases, which I use to help offset the costs of blogging and video production.
