A major disadvantage with an ironless DC motor with a combination of gearboxes results into lower overall efficiency. The use of a gear unit is mainly used because it can reduce the overall efficiency. Precise control is achieved due to the gear backlash with greater effort or an expensive backlash-free gear unit that can be used.
But the advantage also can overcome the disadvantages, as per the installation situation, long, narrow motor-gearbox units or flat motors that can be used to overcome such situation. However, another advantage is the availability of smaller dimensions. DC motors can be operated with high voltage and the currents can remain lower in absolute terms.
The required cable is a cross-section, shields, and controllers can also be a smaller dimension where cost, weight, and installation space can be saved.