I'm sided with the majority here, Crimson is much more desirable to have in a world. The items you get dominate what you can get in the corruption, the layout makes it very easy to navigate though the pre-hardmode mobs can be slightly harder, mainly the Blood Crawlers.
Crimson Armour >>> Shadow Armour - Crimson has 2 useful effects and is not tied to melee
Blood Butcherer/Tendon Bow >>> Light's Bane/Demon Bow - Surprisingly high difference in stats
Ichor >>> Cursed Flames - Defense reduction combines with weapon dps much better than damage over time
Vampire Knives >>> Scourge of the Corrupter - Lifesteal is essentially godmode
As for the themes I do enjoy them both, it is a close tie between them in that aspect, including the music and visual looks.