Huh? Those series look completely different? Code Geass has sharp lines and a neon palette similar to many modern mecha anime, whereas Girls und Panzer has sof

Huh? Those series look completely different? Code Geass has sharp lines and a neon palette similar to many modern mecha anime, whereas Girls und Panzer has softer artwork and a more muted pastoral palette, similar to many highschool sports anime. And while neither series fits perfectly into those categories, I'd still expect it to be a good predictor of preferences. Indeed, while there are some outliers, you can get a pretty good idea what an anime is like from its poster image, which is not really surprising because they're made to appeal to their target audience.