The amount of content produced in such a short amount of time for Terraria is quite amazing compared to Minecraft. They've released very large, content filled, fulfilling updates which actually improve the game a lot and add more things to do. However, these are two people working on one game in their spare time, not a full time company who's working on multiple projects and most likely working very hard. Another thing to note, is that Terraria is coded in C# and is also 2D, so the effort required to add content may not be as equal to adding content into Minecraft, however, that is debatable depending on the coder's proficiency with the language.
Just my thoughts on the subject, that's all. I for one really have enjoyed the Terraria updates. They are very content packed.