It depends on the purpose. For everyday wear, 14K is the better practical choice — it is harder, more scratch-resistant, and more durable than 18K. For maximum richness of color and purity, 18K offers more gold content (75%) with a noticeably deeper warm tone.
After 30 years, I sell far more 14K than 18K, and the reason is always the same: people wear 14K. 18K is softer because it contains more gold and less hardening alloy — and gold's softness is a physical constant, not a manufacturing deficiency. A beautiful 18K bracelet worn daily will show surface wear and scratches faster than the equivalent 14K piece. For a ring worn on the dominant hand, for a bracelet worn with daily activity, or for a chain worn constantly — 14K is the smarter durability choice. 18K shines for pieces worn occasionally or for maximum visual statement.
My recommendation: choose 14K for daily wear jewelry — chains, bracelets, everyday rings. Consider 18K for special-occasion pieces, engagement settings where purity matters, or when you specifically want the deeper color 18K produces. Both are genuine fine gold; the choice is durability preference, not quality.