However they are also different. Twilight likes literature while Rarity is more into visuals. Rarity also understands that a little bit of organized chaos is essential for creativity while Twilight only belives in organization and efficiency. Twilight is simple and straight to the point while Rarity is extravegent. Twilight also doesn't try to show off but Rarity does to an extent.
Just some thoughts. I wish the show went more into detail about their friendship because they are both similar and different.