Oh your vanity Shifty
A hi-viz won't make you be seen, it can HELP you be seen. If you ride differently or thinking you are safer because of the hi-viz, then you have defeated its purpose. It's just one more thing in your arsenal of safety measures.
Other thing with hi-viz, or any clothing - will you stand out from the background. A yellow hi-viz won't make a massive difference against light greens behind you, and if you've a light sky behind you then a dark outfit might help you stand out more. In summer, for example, I'm more likely to spot a black helmet than a white one.
So yes, do wear one, it might help, and probably will do, but don't rely on it, rely on good effective observations and good forward planning (remember that Plan B if Plan A goes tits up).