Using Claydol GE as a comparison, Pidgeot is better where Claydol is not
Your Custom Deck Rexs cards deal with a lot of important strategies for any trading card game: raising the strength of your attackers, searching for what you need, and interrupting your opponent
On the other hand, there are then heroes who weren't especially powerful or plot-important in their home games but are extremely meta-relevant here, such as Karla or Flayn for example
Research your card, and if that isn't there in any of the pictures of it, then you might have a really rare card that could be more than $100
That means Chikorita, Cyndaquil, Totodile, Snivy, Tepig, Oshawott, Grookey, Scorbunny, and Sobble make up the nine possible illustration rare-style promo cards
Norin the Wary might use this as an expensive wincon, though