A friend sent me an email today that I think is very worthy of sharing. He is a twice retired POlice Officer, graduate of the elite Rogers Shooting School, and very seasoned firearms and tactics trainer.
What is your overall opinion of competition preparing you for a real gunfight?
I published my response on my Patreon page, which is generally limited to my subscribers there. It’s an important topic so I decided to make it publicly available. https://www.patreon.com/posts/33975252
tacticalprofessor 
Competition can certainly help keep your weapon handling & marksmanship skills up, But as far as Tactics & Techniques not so much. Both USPSA and IDPA have a lot of rules that are designed to enhance the ability to score the contestant and are useless or even dangerous in real combat. That being said I participate in both.
SGM Robert J. Fleming USA (RET)
Most people who poo-poo the idea of integrating competition into defensive training believe that competitions are there to teach us how to run through a stage with no errors.
Those people are wrong.
What competition teaches is how to respond when our plan goes to hell in a hand basket on us. Whoops, I needed three extra shots on that last array. That messed up my reload strategy. That popper didn’t fall, now what? Yikes, I already shot that target from the other side of the stage, time to change my plan.
The real value of competition is that it helps us learn how to solve problems while moving around with a gun in our hand.
And isn’t that what owning a defensive pistol is all about?
There are many types of training and practice that can help your be better prepared for a gunfight and I do not think any of them are the cats meow, the holy grail, the one thing that it and it alone will get you optimally prepared. Each has advantages and disadvantages. In it’s basic form competitive shooting is one of the most accessible and economical ways for a shooter to get repetitions drawing from a holster, engaging multiple threats, avoiding the shooting of non threats, shooting while moving and shooting from different positions. Most firearms training does not even offer those opportunities in a single setting and the ones that do are too expensive for most folks to engage in on any type of regular basis. Local matches however offer that opportunity for a modest fee, usually under $20. While you have to stay within their safety rules it is a great way to practice what you have been taught in firearms classes.
Perfect timing on this question. I’m getting into USPSA next week. I think with barriers and shooting from different positions under pressure certainly has to enhance your muscle memory and make you a better all around shooter. I also think it will help in self defense situations along with situational awareness.