Pulse waveform

[estim4fun]

I can see on some transformer discussions the pulses, positive and negative, are not beautiful squares.

Sometimes, there is a space in between.

Does it changes something to have
* 150uS positive, 150uS negative and 1.7mS none (at 500Hz input)
or
* 150uS positive, 150uS none, 150uS negative and 1.55mS none (at 500Hz input as well)