If your server already runs Paper, you have already made the performance-sensible choice. The next question people usually ask is whether Purpur is worth switching to on top of that, and the honest answer is: it depends entirely on how much you want to tweak vanilla gameplay itself.
Purpur is a fork of Paper, not a competitor to it
Purpur does not replace Paper's performance work, it builds directly on top of it and inherits every optimization Paper ships. So this is not a performance-vs-performance comparison, Purpur is at least as fast as Paper in practice. The real difference is configuration surface area.
What Purpur adds that Paper does not have
Paper deliberately keeps most gameplay mechanics vanilla-accurate and only exposes performance and moderation-related settings. Purpur goes much further, adding config toggles for things like mob behavior, ridable mobs, hostile mob AI tweaks, and dozens of small gameplay mechanics that Paper has no equivalent setting for at all. If you have ever wanted to tune something about vanilla Minecraft's behavior and found there was no plugin or Paper setting for it, there is a decent chance Purpur added one.
What you give up
Nothing in terms of plugin compatibility, Purpur plugins are Paper plugins are Spigot plugins, the API chain holds all the way down. The real tradeoff is scope: Purpur is a smaller project with a smaller contributor base than Paper, so if you hit an edge-case bug, the fix may land slower than it would upstream on Paper. It is also one extra layer between you and the most-tested, most-battle-hardened build in the ecosystem, which matters more on a large production server than a small community one.
When to make the switch
Switch to Purpur when you specifically want its extra gameplay toggles, want to fine-tune mob or world mechanics without installing a plugin for each one, or you are already comfortable troubleshooting a slightly less mainstream server jar. Stay on plain Paper if you want the most heavily tested, most widely documented option and have no specific need for Purpur's extra settings, plain Paper is not "missing" anything for a standard survival or plugin-driven server.
Trying it out
Switching between Paper and Purpur is just a version selector change on most hosting panels, worlds and plugin data carry over untouched. Tick Hosting's panel lets you flip between them in a couple of clicks, including on the free plan, so you can trial Purpur's extra settings without committing to a migration. Explore the options on Tick Hosting's plans page.