A query on restrictor plates/slides.

The conversation on restrictors came to light yesterday and left me hanging with a couple of unanswered questions.
I was always under the impression that the restrictor slides (with the hole drilled) that my SV has were preferable over the manifold washers, only allowing the slide to rise a certain amount, as well as slower than usual, thus limiting fuel rather than air.
Now apparently this would make the engine run lean, by restricting fuel not air, and wouldn't be favourable at WOT unless smaller diameter needles were also implemented to allow more fuel for less slide movement to balance the mixture (surely a similar result to derestricting?)
The washers as we know are in the manifold and limit the air into the chamber, but they do just limit the air, Being at the end of the carb surely means that the unrestricted air coming into the carb (seeing as the restriction isn't until the manifold) would suck effectively too much fuel by the time it got to the chamber making it run rich; too rich? Or is the amount of air drawn into the carb (not the manifold) directly reduced by the presence of the washer?
Hope this makes sense... It's been sitting there all day and I can't quite work it out
Thank you
Mike