It totally depends on the user and varies from mask to mask. A strap system is designed for those who cannot find a suitable fit across the market. These are designed with vertical and horizontal adjustments that let you set it as per your head size and comfort level. In contrast to this, if you are someone who feels comfortable with an already contoured fit and feels more at ease, you can absolutely go for that one. You can also find some particular mask that provides you with great customization.