A playlist works best when the format is simple
A self-managed playlist can fit a small, relaxed reception with few formal moments and a trusted person willing to operate the system. Music should be downloaded locally, organized in order, and available on a backup device.
Someone still needs to manage volume, pauses, special dances, announcements, and unexpected timing changes. That responsibility should be assigned before the event rather than handed to a guest at the last minute.
A DJ adds active timeline and room management
A staffed DJ can adapt music to the room, coordinate introductions and formal dances, manage guest requests, make announcements, and work with the planner when timing changes.
DJ and MC support is especially useful when the reception has several formal moments, a broad guest mix, or a strong dance-floor priority. The sound system is then operated by the same person managing the music.
Compare responsibility, not just equipment
Ask who creates the final music plan, owns the playback device, carries backups, operates microphones, handles announcements, responds to schedule changes, and troubleshoots the system.
A hybrid plan can also work: the couple provides key music preferences while the DJ manages flow, mixing, requests, and the run of show.