Is 16GB of RAM worth it for a Minecraft server with 5 friends?

Yes, upgrading to 16GB will reduce lag spikes by giving the server more headroom for chunk caching and garbage collection, which is the main cause of stutter. With 8GB, your server and client fight over memory, causing pauses. 16GB spreads those pauses out, making them less noticeable. It’s the cheapest upgrade for smoother gameplay, but won’t fix a slow CPU or hard drive.