While the evolution between Porygon and Porygon2 is perfectly reasonable, the evolution between Porygon2 and Porygon-Z is strange and, in some cases, detrimental. The Pokémon’s totals stats barely improve from 515 to 535, and the balance of the Pokémon completely changes. Porygon-Z has higher Special Attack and Speed than Porygon2
but lower Defense and Special Defense. Whereas Porygon and Porygon2 possess higher Defenses than Attacks, Porygon-Z follows the opposite pattern, causing the final evolution of this Pokémon to completely differ from previous forms.
If players have trained Porygon2 due to its high Defense, they’ll be extremely disappointed when they discover the Pokémon’s final form. Regardless of whether you prefer an offensive or defensive Pokémon, Porygon-Z’s stat increases are so minimal that evolving Porygon2 often does more harm than good.