I know that the Pokemon Fan Club was active from April 2000 to December 2002.
There is a comment from an older thread showing a flyer about the Get points.
Seems that the most common methods were only awarded 10 points each (attending events, post card, purchases). Apparently, you could write articles which I assume earns more than 10 points if published. So, it wasn’t easy to obtain points.
I feel that it depends on how popular the fan club was at the time but I assume if it was popular, they wouldn’t have shut it down and restructured/rebranded into the PLAY club in less than two years. So, I would probably lean towards the Porygon being rarer due to how difficult it was to obtain at the time.
However, the Pokemon Company may have printed hundreds of thousands of copies of the club promos for distribution and for all we know, they could be sitting in abandoned boxes somewhere. Of course the same could be said for the Masaki promos.