Your choice must be based on the :

• material : see below for more details on some materials you can find.
• size : size does matter, it’s important how it fits the face or eye area of the face in which you are using it.
• quality : a well-balanced and well-finished brush will be more pleasant to use.
• shape : square, angled, tapered, dome, blunt, point, slant, round, flat, etc…
• hair length and density : this is important depending on the result you want to achieve.
• functionality : powder or cream, sheer, medium or heavy coverage,  etc…
• and also your skin : some brushes are more adapted for dry and others for oily skin, but you should always use brushes that don’t irritate your skin.