I'm building a news website with a lot of traffic, but the main functionality is reading individual articles. Should I opt for an NVMe or SSD disk for my server?

Who cares about the type of disk you use? It's not like it's going to make a huge difference in the grand scheme of things. What matters most is the quality of your code, the efficiency of your database queries, and the scalability of your architecture.
If your website is slow, it's probably because of some poorly optimized code or a bloated database, not because of the disk type. That being said, if you really want to optimize for performance, go with NVMe.

Assuming all variables are held constant, NVMe is poised to outperform SSD-SATA due to its significantly reduced latency, thereby rendering it a more viable option for applications necessitating rapid data transfer.

It's crucial to grasp that NVMe typically interfaces directly with the CPU via PCI-E lanes, thereby minimizing latency. However, certain motherboard configurations may employ a bridge chip to connect individual PCI-E slots, which can be discerned by scrutinizing the motherboard's specifications. Notwithstanding this, NVMe's performance will still surpass that of SSD-SATA.

The primary bottleneck hindering SSD-SATA's performance is its bandwidth limitation, capped at 550 MB, compounded by the presence of a SATA controller interposed between the disk and the processor. This intermediary controller introduces additional latency, thereby impeding data transfer rates.

Conversely, NVMe and SSD-SATA often employ identical memory chips, underscoring the notion that the disparity in performance is largely attributable to the interface and architecture rather than the underlying storage medium itself.

In scenarios where high-volume web traffic is anticipated, a traditional Hard Disk Drive (HDD) can suffice, offering a cost-effective solution for handling moderate data transfer rates. However, when traffic surges and Input/Output Operations Per Second (IOPS) become a bottleneck, a Solid-State Drive (SSD) is likely to be a better fit, providing faster data access times and improved overall system responsiveness.

Nevertheless, for applications that demand ultra-low latency and high-throughput, such as high-traffic e-commerce platforms or real-time data analytics, an NVMe (Non-Volatile Memory Express) drive is the clear winner, offering unparalleled performance and scalability, thanks to its optimized protocol and multi-queue architecture.