DTC is just a different flavor of vector control in relation to FOC, but is more tricky to implement, as far as I understand and is the reason why FOC is the more commonly used method.
Although the vector control algorithm is more complicated than the Direct Torque Control (DTC), the algorithm is not needed to be calculated as frequently as the DTC algorithm. Also the current sensors need not be the best in the market. Thus the cost of the processor and other control hardware is lower making it suitable for applications where the ultimate performance of DTC is not required.
Everytime BV tried to tutor me about FOC he said that the reduction of power losses in BLDC vs. FOC exist but are very small. Meaning the EFFICIENCY of FOC is higher. I interpet that into more watts are used to the motor instead of turning into heat. If this is even meassurable @ momentarly consumption in an eskate application. is very hard to tell.