Sorry, you're not looking at the old frame. With vsync off you're looking at the last frame, although sometimes frames overlap in buffer and sometimes incomplete/overlapped frame/frames can be pulled, hence you got some artifacts like tearing, etc.
With double buffering and page flipping sync that problems is pretty much solved and I haven't seen any tearing, shearing in a very very long time.
As for the performance, unless your system can keep up with monitor refresh rate at all times, vsync-on will degrade your overall frame rate due to timing issues.
Believe what you want, Bighorn. In addition to the shearing, tearing and artifacting, one of the other ways that
edit-> having VSync off <-edit will affect most 3D games is to allow what's displayed to "lag" behind what the game engine internally "knows" to a varying degree dependent upon the speed of your computer, video subsystem, and the complexity of the algorithm in the game.
Do an Internet search for VSync and mouse lag, PrerenderLimit and/or Render no more than (x) Frames ahead, and specific to flight sims, Vsync and "rubber bullet syndrome".
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