Both were vital parts of my childhood. I personally don't have a preference/ They're both fun as all hell.
Terraria = more hardcore, faster paced, more combat oriented.
Minecraft = More chill and relaxing. More PvE based, a bit more casual.
Also, I personally think the 2 don't really compare all to well. Kinda like Apples to Oranges, sure they're both sweet, and are fruits but that's really it.