Gsync helps with variable refresh rates so yes it will give a smoother experience.
With Vsync off, your FPS in many games will bounce around depending on game of course, it could bounce from 30FPS right up to 100+ and back or in the middle bla bla you get the idea. A monitor with just 144Hz will help smooth out a lot of it but it will still tear.
Then you enable Vsync on a non Gsync monitor to stop screen tear, you'll get fixed refresh rates depending on your game. on a 144Hz panel the next drop in Hz is half, so the refresh will dramatically change from 144Hz down to 72Hz then again to 36Hz if you couldn't sustain 72FPS.
With Gsync, its variable Hz so what ever FPS your GPU is producing is what you will see on screen.
So yes Gsync is worth it.