Apple's new OS is coming this fall, and here are some of the new features you can look forward to. I watched the live streaming of the WWDC17, and VP Federighi demoed Apple's new file system, AFPS. It was impressive to see how much faster it will be than the very old file system Macs now use.
Among many other enhancements, Apple states that Safari has been improved and will be the fastest browser going. All in all, High Sierra will be a nice upgrade, and free to boot.