A rebuttal to Snipe's arguments last night.
Point one: No poison.
What? You actually care about whether or not a game has poison mechanics? That's like saying "I can't be set on fire, this game sucks." I'm sure you see how ridiculous that is.
Point two: Update numbering.
Okay, so Minecraft is almost at version 1.8, while Terraria is up to about 1.0.6, correct? Oh, how terrible, Redigit updates faster than Notch and Jeb. He also has a much simpler job, and piles in a large number of slight modifications to existing objects-- take swords, for instance. I don't know the exact way it's coded in for that game, but considering use of an object-oriented programming language, you could probably add a new weapon with 25 lines of code or less. Notch could do the same, but he doesn't; instead, he focuses on creating fully original content that recycles very little code. A similar concept applies to creatures.
Look at mobs in Terraria. Zombies, skeletons, angry bones, and so on all have almost exactly the same AI, with differences only in appearance, damage, and speed. Apply the same to meteor heads and cursed skulls, along with all the different slime variants. To add to one of these "categories," a developer could simply instantiate a new object, change up a few variables, and there you go. Again, Notch could do this too, but chooses to change things up more. Creepers, zombies, skeletons, spiders, and slimes all have totally different AI code. Four of the five walk, but how they all react to the player is totally different.
Slimes and zombies are fairly simple; they just charge the player and attack head-on. The biggest variance here comes from the code that makes slimes split if they are killed by an attack that's too weak.
Skeletons and creepers will both begin to strafe counterclockwise around the player once at a certain distance. However, skeletons fire arrows from afar, whereas creepers come up close and explode.
Spiders are somewhat similar to slimes and zombies, in that they attack head-on. However, they will leap at the player once they come close, and are capable of climbing walls. This requires not only an addition to the code for the mob (saying that it can climb at all,) but also an exception in the damage code, to somehow tell spiders not to be knocked back when climbing cacti.
Point three: textures.
Okay, so in Terraria maybe you don't have to leave everything as a square. So it's got big fancy curves and whatnot-- as above, who cares? Part of Minecraft's charm comes from the blocky visuals, which is why a lot of players refuse to make use of a high-resolution texture pack. On top of which, let's just take a quick look at the file for Terraria's terrain tiles. Each variety of tile will have anywhere between 12 and 50 sprites, just as a quick estimate. For Minecraft, you have a maximum of six, all of which will be in use at any one time. (The one exception is chests, which have a large tileset because of the way they spread out.) This makes actually drawing in new textures much easier, to the point that some people have done it by hand.
Well, that's that. Thoughts? Arguments? I'd like to see you come up with a way to outfight me on this.