Terraria > Minecraft
(maybe not in the long run tho, making huge stuff in minecraft is pretty tight)
I played the **** out of Terraria until I pretty much did everything. Killed all three bosses, explored the underground jungle, the underworld, got the best armor and weapons, etc.
I haven't played since it first came out and I know they released a bunch of new content, so I might start fresh one of these days. but yeah it got stale once I got the best armor. there really wasn't anything to do anymore and I was one shotting everything.
you nailed it though, in the long run it isn't better. when you first start out there is a ton of content and more to do as far as adventure goes, but once you get the best items there really isn't anything to do anymore. Minecraft has way more longevity. with that being said, Minecraft could take a lot from Terraria. One of my favorite things about Terraria is the incentive to explore. for instance, the random chests around the world that have unique items in them. I love stuff like that.