Answer: G-Sync is definitely worth it if you have an NVIDIA GPU and are looking for a monitor with a high refresh rate. If you've ever thought about getting a monitor with a high refresh rate, like a 144Hz or a 240Hz one, you've probably noticed that a fair number of them come with something called G-Sync.

Does G-Sync affect performance?

G-Sync, as far as I know, had virtually no impact on FPS. G-Sync helps to reduce screen tearing and ghosting. It also will make any fluctuation in FPS look smoother.

Does G-Sync matter at 144hz?

So to answer your question, YES there is a difference between a 144hz monitor with and without GSync. If your monitor does not have GSync and your GPU is unable to produce 144FPS, you will notice tearing.