The tech-heavy Nasdaq 100 is the best performer but more risk-averse investors may prefer the more broadly diversified S&P 500.

The NASDAQ-100 is widely followed as a measure mainly of the big tech and social media stocks that make up the index.

The Nasdaq and S&P 500 were rattled by claims by China's DeepSeek that its AI assistant uses cheaper chips and less data than leading models, but performs equally well. A surge in DeepSeek's ...