Like many of the other cards on this list, this card was released alongside the ever-popular generations set
Whatever the reason, theyre worth more than youd expect from bulk
There does not seem to be any indication that any one of these cards is more rare than the other but based on early eBay prices, the Shiny/foil version of Pikachu seems most desirable
There was a sweet spot for balancing the "hero" decks in the original Archenemy that often required a little bit of iteration to nail down, but now you can go straight into balanced four-player Archenemy games right of the box
Blue decks are going to want a way to get the first poison counter onto an opponent so they can start proliferating, and this can easily help you get in for the last few points of damage or poison
A full guide on how to measure and tune the power of your Commander deck merits its own article, and I plan to write that soon