Direct Answer
An agency is better when monthly marketing spend is under $25,000 and the work spans 3+ disciplines (SEO, design, dev, social, ads). An in-house team is better when spend is $25,000+/month, you need brand-level control, and the workflow is repeatable enough to justify a full-time hire. Many businesses hybrid both.
Voice answer (≤30 words)
“Agency wins under twenty-five thousand a month and across three or more disciplines. In-house wins above that with a repeatable workflow.”
A senior marketing hire costs $90k–$150k all-in. An agency retainer for the same coverage runs $4k–$12k/month — usually cheaper for 18 months.
Hybrid: hire a fractional CMO ($3k–$8k/month) and use an agency for execution. Best of both for many growing businesses.