I want to make brioche and have seen several recipes. Some use a sponge and some don't. Is there a difference in the end product (flavour, texture, look...)?
In general, preferments of any kind are used for several reasons:
With all of these reasons the choice is totally yours. You will see a definite improvement using a preferment, especially with something like brioche that should be rich and flavorful. If you are in a hurry though- a fast brioche would be better than none at all.