It's the double yields from ore. There are two other ways to get more yields, but these two can be set up sooner.
Either one requires something to power it, so you'd need an engine (either Stirling or the TE Steam engine to start with) for the Pulverizer OR Induction Smelter, or you'd need a Generator for the Macerator. Both setups require a fair amount of metal and some Redstone. The TE stuff requires Gold, but... when you need to find Redstone either way, Gold isn't going to be far behind. That considered...
The Engine + Pulverizer (or Induction Smelter) combo is cheaper to assemble than the Generator + Macerator, and in my tests, the Pulverizer will get a lot more done with your coal/charcoal than the Macerator will. Since it combines two steps, the Induction Smelter will get much more done than either of them for the same amount of fuel. The Pulverizer also has a 5% or 10% chance for each ore (except Iron) to give you an extra piece of dust for another metal. Gold can be found in Copper, Iron in Tin, Silver in Lead, etc. The Macerator does not get any bonus dust.
The catch with the Induction Smelter is that it requires Sand as a catalyst and it doesn't get the extra dust that the Pulverizer does. Instead it gets slag for smelting into "Rockwool," wool that behaves like stone where fire and explosions are concerned.
That said, you will eventually want a Macerator. It has some utility uses that the Pulverizer does not, one or two things it does better, and, unlike the Pulverizer, works really well in combination with a Rock Cutter or other Silk Touch pick. In many cases it rivals Fortune III (the enchantment does manage to beat it out for Diamonds and Coal), and it does work on Uranium and Iridium, which Fortune does not.