VSYNC VSYNC VSYNC Help

Hi. When exactly is it advisable to turn VSYNC on? I play DOTA 2 with VSYNC off and I kinda notice turning it on while playing a single game and I felt better gaming performance… or is it?

Turned off: 70-90fps with 100+ max

Turned on: 59-60fps with the lowest of 56

I have a Samsung SyncMaster monitor (not really a gaming monitor) with 1366 x 768 HD resolution (not FULL HD) and 60Hz refresh rate.

The problem that I encountered now is that when I’m in the GAME MENU of Dota 2, I get a locked FPS count of 30 (HALF MY VSYNCed fps count)

My Maximum fps count is set to 120.

Enlighten me pls. Thanks.