My take is, there is no training that replicates true, life or death consequences. Really unless there is some horrible neglect act, everyone knows they are going home after a training session. Even when you consider force on force training, everyone knows they will go home, abit there may be a few bruises on body body and ego, but very seldom are body bags put to use.
With competition, you learn to run the gun, and with 3 gun, IDPA etc you learn to move, and the "cover" may be flimsy 1/2 inch plywood, you do learn to make use of cover, and even in training where cover was used it was plastic barrels, and 1/2 inch plywood barricades in any course I've attended.
Competition can be cost effective, attend the local IDPA match, entry fee is $15, and you might run through $50 worth of ammo, plus gas and lunch, you'll likely have some change out of a C note.
Formal training can get expensive, it can run from $150-$200 a day, you'll likely blow through an entire case of ammo, and unless it is local, you'll have motel etc, It is not hard to get north of a $1000 pretty quick.
Now if you are the average guy, with a family and house payments it is a lot easier to come up with a $100 than a thousand, and it sure beats just going to a commercial range where you plant your feet, and shoot all from the ready, at a rate of fire set by the range, now no bitching, they are at the mercy of the insurance companies, and while you may know your way around your smoke wagon, there will be 95 others that visit the range that are not, and you only have to go to the local range to see that.
I'm not saying you shouldn't take training, in fact you really should, a good instructor weather he is local, regional or nationally known, will tune you up, he or she will advise on ways to be quicker, and more accurate. they will see the mistakes that you do not realize you are making.
There are merits to both training and competition, and it is a matter of finding a balance, is competition tactical? Yes & no, a match can have tactical aspects too it, but there is nothing tactically sound, of one guy going up against 40 bad guys either. For training a lot of drills are based in some way on actual gunfights, and they can be timed to induce stress, but it is a different stress, and in classes you may be timed but you don't always know how you stack up even with those you are attending with.
Competition does force you to think, training often does not. In a match you have to think how you are going to shoot a stage, yes I know gunfights are unpredictable. But in a lot of training you are told exactly what to do, in many of my classes, as we get farther into the class, I often describe the drill, then get ask by students how do I want them to do it, and my reply is it is your gunfight, figure it out.