The correct motor is the vital heart of the model. Quality and power are paramount. Why cut costs with poor quality? Mashima motors have limited power. In the smaller models I fit the Japanese Cannon. This is one and a half times more powerful than the Mashima.
In the larger models both 7mm & gauge 1 I fit the excellent and proven ABC helical start, multistage gearbox, coupled to a Swiss Maxon motor, this setup is two and a half times more powerful than the Mashima. Larger motors are fitted in the Gauge 1 models.
The Maxon motor is currently being used by NASA to power the Mars probe. They must know quality.