A ring flash can be useful for portraits mainly in two ways:

1. On-axis fill light: It works very well as fill when your main light is high and hard. Because the ring flash is centered around the lens axis, it can open up deep eye-socket shadows (“raccoon eyes”) without creating a second obvious shadow direction.

2. A distinctive look: Used as a key light, especially with the subject near a wall, it gives very even frontal light and can create a recognizable halo/feathered shadow behind the subject. This is a deliberate, bold style often seen in editorial, glamour, or alternative portraiture.

Other benefits include circular catchlights/specular highlights, which some photographers prefer over rectangular reflections, and practical use where bounce flash is difficult, such as outdoors or in rooms with high, dark, or colored ceilings.

Disadvantages:

• The look can be flat or harsh if overused.
• It is very stylized, so it may not suit every portrait or wedding situation.
• For many event uses, bounced flash can look more natural.
• Some of the “softness” and evenness can be approximated by other diffused flash modifiers at lower cost.

So, ring flash is best when you want clean on-axis fill or a specific fashion/editorial effect—not necessarily as a universal replacement for bounced flash.