TTL is most useful when the flash-to-subject distance or scene is changing and you need a usable exposure quickly.

For fixed off-camera setups, manual is usually better: once the lights and subject stay in place, exposure is repeatable from frame to frame and TTL offers little benefit.

TTL helps when:

• the subject moves closer/farther from the lights
• multiple lights and distances change rapidly
• you must work fast with little or no test shooting
• the flash is handheld or placed where adjusting manual power is awkward
• you may only get one chance at the shot

A common example is fast-moving event work, such as a reception dance floor, where manually recalculating or resetting several flashes would be slow and frustrating.

TTL is often faster and safer for getting a decent first frame. It does not necessarily mean less control: instead of setting flash power directly, you usually control brightness with flash exposure compensation. So the control is different rather than absent.

In short: use manual for consistency in stable setups; use TTL for speed and changing conditions.