Existing pull rate data from Mega Dream ex that includes Japanese prints of these Mega Attack Rare Pokemon cards (with their attacks written in English) suggest that these cards are a step in-between Illustration Rare cards and Special Illustration Rare meaning more rare than IR cards but not as rare as SIR cards
You do want to make sure youre playing it in a deck that can realistically get delirium, though
Charizard Pokmon cards can vary widely in terms of price
A well-drafted deck with an appropriate sideboard can alleviate this problem, but in most scenarios, you don't want to include cards like Disenchant in your main deck unless you are certain that you are playing in an artifact and enchantment heavy meta
During the opponents turn, it can protect itself from card effects
To understand why Umbreon VMAX Alt Art is so valuable, you must understand the Pokemon singles market its drivers, and nuances