ledc functions are left aligned and MCPWM are center aligned what makes a big difference.
One of the most important reasons is the difference of the current waveform the two singals produce.
Here is an image of center aligned pwm signal
And left aligned PWM
This is just a simple example.
In general the reason we are setting the voltage to the motor is because we want to generate torque, which is proportional to the current of the motor. This basically means that we would like to control the current. Current has its own dynamics, and it cannot follow the fast changes of the PWM signal but it more or less filters the mean value. You can see that on both images in yellow.
Now, when you have center aligned PWM signal the signal the resulting PWM signal the motor sees (A-B) in green will be balanced in time and divided in two, which will maintain the minimal variance of the current. When you have the left-aligned PWM you will have a lot loger HIGH times and LOW times making the current waveform much more oscillatory, what makes the motor torque more oscillatory.
Due to these long stationary values, it is even possible that the current drops to zero at some point, what would mean that there would be no generated torque on the motor for some time.
As @Owen_Williams said if the PWM frequency is high enough these effects are less visible. But in general, current dynamics are under 1ms so you would need to go above 50kHz or even more in order to filter this behavior, what is in many cases impractical.
Therefore in reality especially for lower duty cycles the difference can be substantial.
The other reason why center aligned PWM is used, is because of the architecture of the bldc drivers.
In our case we are controlling the set of upper mosfets (PWM 1,3,5) and lower set (PWM 2,4,6) is generated in BLDC drivers directly, essentially they invert the PWM signal sent to the upper ones. They perform much more efficient when you change only one signal at the time. Only one set of mosfets at the time. For the case of left-aligned pwm, you will be always changing all three sets of mosfets at the beginning of the PWM cycle.