Charizard obviously has had vastly more success as a mascot but I wonder if thats owed more to Pokemon's fame and Charizard's role as an early game, very accessible dragon-like partner coinciding with their appeal towards nostalgia. However his simplicity gives a lot of room to project personal touches onto said partner. Design wise though his only major standout feature is the flaming tail and unique body shape.

Greymon on the other hand arguably has more iconic features like the helmet and stripes, he has a design very typical of the era's kaiju, specifically Gomora from Ultraman.
Though in fairness, Charizard himself was also playing trends by mimicking the dragons of Dragon Quest so closely.

But which one would you say has the better design in the end?