The choice will be relevant based on the rewards you consider offering.
The presale objective is useful if your aim is to offer a specific product and that you need to presale a minimum number of X copies to start a production or keep your activity going. In that case, the logic is: one contribution = one presale.
The financial objective is the most chosen one. It offers the ability to create various rewards, collect more money and allow smaller budgets to support you, as the minimum reward starts at just 5€. Keep in mind that you will need to offer a minimum of 4 rewards.