An in-browser VPN extension is innately contained to the browser it’s installed to, which has several benefits:

• high-bandwidth activities outside of the browser, such as software updates and game downloads, which many people don’t consider part of their privacy profile, won’t be limited by the speed of the VPN
  • this is also possible with split-tunneling, but that requires more configuration, and not all VPNs support split tunneling on all OS environments
  • the bandwidth savings are a big reason why most VPNs create browser extensions and encourage their use, as bandwidth use from web browsing is always going to be smaller than full system bandwidth
• different browsers or browser profiles can be configured to use different VPN endpoints, while most system-level VPNs can only select one endpoint for the entire system
• setup and configuration will be more OS-agnostic; setting up a system-level VPN properly on Linux can be more difficult than Windows or MacOS depending on the distro and system config
• running the VPN at the browser level usually takes less resources than at the system level, so on very old or very weak systems, it may be the best option

Of course, if you’re downloading actual Linux ISOs and want to avoid a nasty letter from your brain-dead ISP that thinks all torrenting is illegal, or if you just don’t want your ISP to spy on you and sell what it learns to data brokers, installing the VPN at the system level is a great option. Remember to bind any torrent software to the VPN to prevent leaks ;)