Mike,
The situation I am talking about with the hi-viz is in a situation where a driver doesn't look properly. (shock horror it does happen!
) They may have glanced in your general direction, but not looked properly. In this situation I am certain that a bright yellow against gray blob (or reflective blob) would be more likely to be registered (just enough to cause a hesitation and possibly a second look) more than a black against gray blob. It could just be enough to make a split second difference.
I think being like a vehicle is fine for experienced cyclists like yourself Mike. You probably do act as a vehicle. However, for the masses this probably doesn't help. They are more likely to wobble or veer off to one side or another in a way that a car wouldn't be able to do. If they appeared as a car then this could completely take other drivers by surprise.
I suppose I also don't want to have to blend in. I want to be seen as a cyclist. I am after all proud of the fact that I ditched the car for my commutes! I want others to see me and others cycling in and think, hey, I can do that. Maybe I need a big hi-viz sign attached to my back saying something like 'This is fun, honest!!'
Of course all of this is hypothetical and supposition. In the end I am happy so long as people make an informed choice. At least that indicates that they are thinking 'safety'. That's why I like debates like this, even if it means I think your a nutter to not be wearing some form of hi-viz....