It depends on what you mean by “smarter.”

- **Sherlock Holmes** is usually portrayed as the more **brilliantly analytical** of the two: faster with deductions, broader in scientific knowledge, and more improvisational.
- **Hercule Poirot** is often the more **methodical and psychologically perceptive** detective: he relies on order, logic, and understanding human behavior, and he’s extremely consistent.

**Short answer:**  
If you mean raw deductive genius and versatility, **Sherlock Holmes** is often considered smarter.  
If you mean careful reasoning and insight into people, **Poirot** can rival or even surpass him.

If you want, I can also compare them in categories like intelligence, observation, social skills, or case-solving style.
