Before jumping on any band wagons, it's important to first understand what exact taste and texture that one is looking for. The term preferment can easily be something that is a day old and commercial yeast fermented with a taste complicated by varying degrees of different flours, or it can be a wild yeast starter that is many years old, where a strong degree of sourness is appreciated over at least a 1+ week period.
If you look at ACME in San Francisco, or Artisan Bakers in the wine country where the owner represented the USA baking team in their first prize winning speciality-breads category, you'll see that both commerical yeast preferments and wild yeast preferments are employed. At the Coupe du Monde competition, the weakness of the french flours needed to be offset, and commercial yeast preferment were employed.
The interesting thing is that most people jump into preferments because they are sooo... unhappy with the taste of their flour. If I were to take a dish and dump habenero peppers all over it, then I would definitely transform the taste; but sometimes, I just want a better tasting dish.
Personally, I love the taste of a little "white" whole wheat flour, a brand that Kansas City expects to displace the bitter taste of red whole wheat in the next few years. By taking a 1-day-old commercial yeast fermented "white" whole wheat poolish (1/16 tsp instant yeast for 4.5 oz or 1 cup of flour) and combining that with a high quality bread flour and leaving that out for 3 or more hours until it doubles, I get an outstanding tasting result.
So the first thing you want to ask yourself is what taste and texture are you looking for because it will be impacted by a preferment (e.g., sweet vs. sour, wholesome wheat or rye vs. white, soft vs. a pull). The longer you let your starter sit, the stronger it's role will play.
If you decide to use a whole wheat or rye in your starter, the color and taste will be impacted as well. And once you hit a temp of 60F, you will get bubbles in your dough and a stonger acedic acid (vinegar). Whereas, while leaving it out, it may not be as strong due to lactic acids. Also, by leaving it out at warmer temps, protein-attacking enzymes will work harder to break down the gluten development, and you'll need to stir to increase its strength. Also, the more dry the texture of your preferment, the stronger it can make your end texture. So when asked to leave it out vs. colder temps, it really depends on what you want in taste and to some degree, texture.
Also, don't confuse wild yeast that you can easily create yourself or buy in a packet, with bacterial fermentation that is responsible for the taste. The wild yeast has many advantages, including that it handles higher acidic environments over a longer period of time. But regardless where you buy the wild yeast, the end result is largely impacted by the bacterial fermentation, which is regionally established. Longer fermentations are certainly not always appreciated even by bakeries in the San Francisco area, where sourdough is only 1 of so many varieties that are offered.
The main thing is that you don't limit yourself to just a long-time starter. And don't limit yourself to a single taste. Think about all those wonderful tastes you've enjoyed at bakeries. As a starting point, try mixing King Arthur's white whole wheat flour, for example, which has just over 11% gluten developing protein (25% protein is not gluten development due to bran and germ), with a higher protein King Arthur bread flour or a high gluten unbleached flour the next time your playing with a recipe. The combinations are endless.
