I've shot IDPA this weekend, and there was this one standards / classifier-like stage that I think can serve as a good demonstration of IDPA and USPSA differences from defensive shooter point of view. 4 targets, 3 shots in the body and 1 in the head each.

USPSA > IDPA >>> Static Ranges

IDPA markets itself as somewhat more realistic USPSA, trying get way from gamer race guns and more into everyday carry gear and CCW's interests. In my opinion, both IDPA and USPSA are simply games, or gun-golf if you will and have nothing to do with tactics. But since they both deal with guns and shooting as a skill -- they both can and should be used as a great training tool.

If you compare IDPA or USPSA to regular static shooting ranges -- these games provide a much more challenging, and closer to reality environment. They have human-sized targets, with different zones trying to replicate physiology of an adult male. Stage often require you to shoot on the move, while leaning around walls, crouching, reloading, and other cool stuff. Both games are definitely more dynamic and challenging than single lane static range live-fire practice. So they are learning and skill-improving and testing tools for you as a CCW / defensive shooter. But which game is better?

In my opinion this is going to be USPSA. As you can see in the video, when I shot this stage in USPSA mode I was shooting faster and I didn't have a reload. Let's address the latter first. IDPA has Division Capacity rule, which is 10+1 for Carry-Optics division. Because of that I have to reload, and it throws the timing and the flow of the stage quite a lot. I'm not saying that you shouldn't practice reloads, but this Glock 17 is my real carry gun and I definitely don't want to create a habit of thinking that I ran empty after firing only 10 shots. Also it's much more fun to shoot more rounds without reloading. More fun = better emotions / attitude, and even though it might not sound serious -- these things are actually important in learning. We learn better when we feel safe and in a good emotional state.

Shooting Speed

Now let's talk about shooting speed. To keep this simple -- IDPA has severe penalties for non-alpha hits (heart and major vessels nearby). On a stage like that one Charlie in IDPA will cost me more than 10% of the score. If I shot at my USPSA speed - it would've been even more -- 20%. In USPSA, even when using Minor -- one Charlie (lungs and body) is only 2.5% at USPSA shooting speed. This forces you, even if you try to push speed to shoot slower. Unfortunately slower doesn't always equal more accurate. And it also, in my experience, doesn't provide the best way to improve as a shooter. Add here the fact that most DGU videos that I researched online showed people shooting pretty much as fast as they can pull the trigger -- and it becomes clear that USPSA's Hit-Factor Minor scoring is much better suited for training defensive shooters than IDPA's 1 second per point down penalty.

You might argue that CCW and defensive shooter applications require higher degree of accuracy than USPSA and you won't be able to "miss fast enough" in real life, but the thing is -- Misses and No-Shoot penalties are similar in USPSA and IDPA, while the only difference really is between Alpha and Charlie hits. And in my opinion, considering most handgun calibers terminal ballistics -- there aren't that many differences between Alpha and close Charlie in defensive applications.

So for pure shooting skill, I would say USPSA is a better training tool than IDPA. USPSA stages also usually have more targets per position and higher overall round counts per stage and match, making it a more condensed practice. However, there's something to be said about IDPA's rules and stage construction, that might be interesting for you as a defensive shooter, especially if you only shot USPSA.

Hesitation and Interruptions

In IDPA there a much more interruptions and less flow than in USPSA. You can't drop non-empty mag on the ground in reloads, can advance toward un-engaged target with unloaded gun, you must be aware of positions of cover and it also requires harder focus on alphas in order to minimize penalties. This leads to longer pauses and builds hesitation, while also loading your processing platform a bit more than you already got used to in shooting USPSA. All that lack of flow might sound not like a lot of fun, but for defensive shooter -- it's a good thing. Fighting through hesitation and overloaded processing platform is essentially what allows you to get better and "thinking with the gun in your hand" and ultimately should reduce processing delays in the future.

Additionally, at higher levels, A-class USPSA and M-class IDPA -- I would even say that shooting different games with different scoring systems can make you a more well rounded shooter. If you consider 3gun scoring, USPSA Major, USPSA Minor and IDPA -- they create a sort of a spectrum for shooting speed. Having experience in all parts of that spectrum will allow you to calibrate your throttle control mindset and ultimately make you a better shooter overall. Especially for defensive applications, where you might need to be able to judge distance to threat and the environment to quickly select appropriate response and engagement speed.

Going back to the video, you can see that splits were pretty close, but transitions to the body, and especially to the head took much longer in IDPA, where I tried to be more cautious about getting an alpha.

But if in IDPA I had an acceptable 2 points down, in USPSA I had a Mike on the Head of the 3rd Target. What happened is that I was riding recoil a bit in Body-to-Head transition and on first 2 targets it went great, but on 3rd the target size got small enough, that I needed to wait a bit for the gun to settle in the recoil, which I didn't do on third target, but did on fourth. In IDPA mode I wasn't able to detect that inefficiency, but in USPSA speed it became obvious.

TLDR

So if you have access to both and are new to competition -- I suggest you pick USPSA over IDPA. But if you shot USPSA for a while, you might find some new challenges in shooting IDPA as well.

Video Version

This analysis is also available in a video format on my YouTube: