The difference between a cached and uncached WordPress site can be three seconds. Might not sound like much, but Google measures it and visitors leave. We installed five popular caching plugins on the same test environment and measured.
Test environment
WordPress 6.4 on a Hetzner VPS with 2 vCPU and 4 GB RAM, Nginx, PHP 8.2. Theme was Astra with WooCommerce and 200 products. All tests ran via WebPageTest from Frankfurt, three runs per plugin.
WP Super Cache
Free and simple. Creates static HTML files. TTFB dropped from 1.8s to 0.3s. Lacks database optimization and CDN integration out of the box, but for a straightforward site it's more than enough. Configuration takes five minutes.
W3 Total Cache
Powerful but complex. Settings span eight tabs with hundreds of options. We got TTFB down to 0.25s, but it took half an hour to configure. And with wrong settings the site actually got slower than without cache. That happens more often than you'd think.
WP Rocket
49 USD per year. Works right after installation without changing a single setting. Lazy loading, database cleanup, page preloading, all built in. TTFB: 0.22s. This is the plugin we recommend when the client doesn't have a developer managing the site day to day.
LiteSpeed Cache
Requires a LiteSpeed server (not Nginx or Apache). But if you have it? TTFB: 0.18s. Fastest we measured. Free plugin with CDN integration and image optimization. The problem is locking yourself to a specific server type.
FlyingPress
Relatively new. Clean admin, good performance (TTFB: 0.24s). Priced between WP Rocket and the free alternatives. Lacks the broad documentation and community the older plugins have.
The summary is simple. Most sites: WP Rocket. Tight budget: WP Super Cache. LiteSpeed hosting? The free plugin beats everything else.