This is a fun question that's been debated by mystery fans for over a century. There's no definitive answer, but here are some considerations:

**Sherlock Holmes** excels at:
- Deductive/abductive reasoning from physical evidence
- Disguise and fieldwork
- Breadth of specialized knowledge (chemistry, anatomy, etc.)
- Raw observational power

**Hercule Poirot** excels at:
- Psychological insight and understanding human nature
- Methodical logic ("the little grey cells")
- Drawing out information through conversation
- Solving cases with minimal physical investigation

They represent somewhat different *styles* of intelligence. Holmes is more empirical and scientific; Poirot is more psychological and intuitive. Holmes sometimes misses human motivations that Poirot would catch, while Poirot might overlook physical clues Holmes would spot instantly.

If "smarter" means raw intellectual horsepower, they're likely comparable—both are presented as essentially the greatest detective of their respective fictional worlds. Your preference probably says more about which *kind* of intelligence you value most.

Do you have a leaning yourself?
