Choosing a focus distance or stroke / Choosing a specialty

So many swimmers classify themselves as a "sprinter", "breaststroker", "middle distance", "IMer", etc. Since training can affect the outcome, how can you tell if your talent matches what you're training? To clarify with an example: How can you tell if you're really meant to be a distance swimmer vs. you like distance and you've trained yourself into it? There's definitely something to be said for just doing what you like and going with it. Or to just take an all around approach similar to what is recommended for age groupers. But what if you want to pick something to really throw your focus into? Is there an objective way to decide what distance a person should focus on or what stroke a person should focus on? If you have a specialty, how did you decide?