Most people arrive at the question through cost, which is a reasonable route and the wrong frame. Group is a third to half the price, and that isn’t why you would choose it.
What individual is better at
Anything requiring a specific protocol. Exposure and response prevention for OCD, interoceptive exposure for panic, trauma processing. These need to be paced to one person and individually constructed.
Acute crisis. A group can’t give one member the airtime a crisis needs, and shouldn’t try.
Material you can’t yet say out loud. Some things need one person and a closed door first.
Depth on your particular history. Groups don’t have time to reconstruct anyone’s childhood in detail.
What group is better at
Anything about how you’re with people. The decisive case. If the pattern is interpersonal, individual therapy gets your account of it and a group gets the thing itself. That isn’t a small difference.
Shame. Hearing three other people describe your private conviction does something no amount of individual reassurance does.
Social anxiety. Individual therapy asks you to describe the feared situation. A group supplies it, weekly, with a clinician present.
Loneliness. You’re practising connection with the same people over months rather than analysing why it doesn’t happen.
Feedback. Nobody in ordinary adult life will tell you how you come across. In a group they will.
Being useful to someone. Unavailable in individual therapy by construction.
The honest case for both
A great many people do both, and the combination is frequently better than either — individual work on the material, group work on how the material shows up with people.
Practically, this is also the most common route into group: someone already in individual therapy whose therapist suggests it, or who joins a skills group alongside.
If you do both, tell each clinician about the other. Groups generally want to know, and where the group is part of a programme they will usually coordinate.
The resistance worth examining
The reasons people give for preferring individual are usually true and are occasionally also the reason group would help.
“I wouldn’t be comfortable in a group.” “I don’t want to listen to other people’s problems.” “I wouldn’t get enough time.” Each of these is reasonable — and if the pattern you’re working on is withdrawal, or difficulty tolerating other people’s needs, or a sense that you don’t warrant attention, then the objection is describing the material.
That isn’t an argument that everyone should be in a group. It’s an argument for noticing which of those sentences is yours. The twelve-question check asks some of them directly.