There are two common low-cost ways to drive linear motion: Belt/Pulley or Leadscrews. It seems obvious that belt/pulley can run faster, while leadscrews can take a larger load. But if the machine needs to do any 3D printing, the belt and pulley is the only choice.
The reason is simple: leadscrews do not go fast enough. Take, for example, a common cheap 1/4" x 20 threaded rod on a common NEMA 17 stepper motor. The motor turns at around 300 rpm. At that rate, the drive is moving 15 inches per minute, or 6 mm/s. That's painfully slow, as a decent 3D printers now-a-day can run about ten times as fast. Of course leadscrews can go faster with a multi-start ACME rod. But that drives the cost up quite a bit, and is no longer options in the low cost world.
As a result, all of the 3D printer or 3D printer / CNC combo design I see uses belt/pulley to drive the X/Y motion.