The corruption; because 'im totulli retro dooood' type of guy, plus I feel the Crimson was just a not really worked out copy of the corruption, that EVERYONE would make multiple worlds to get it for better gear.
It annoys me that you cant take an altar with you, given that its a crafting station that your world may one day be without. Maybe we should have craftable altars and shadow orb/crimson heart decorations..Corruption because I like building my main base around an Altar and the Corruption ones look better.
Shadow Orbs look cooler floating around after removing the surrounding corruption
The Shadow Orb item is very useful to me prehardmode since I don't need to carry many torches
The Band of Star Power is far more useful than the Panic Necklace
Eater of Worlds drops one of those useless but cool pets
Scourge of the Corruptor fits my play style far better than Vampire Knives
I import crimson blocks from other worlds anyways so I can get most of the crimson specific items while keeping the Altars and Orbs that are specific to Corruption worlds.