I have no other saber to compare it to and I don't know how to describe it better than use the word "flicker".
Let me use all my English to be as precise as possible of what I experience: there's a tiny "resonance" in the blade when it's turned on. It only can be seen if I pay attention to it or can be recognized in a completely dark room. It looks cool for me but that's personal preference.
When the batteries (4xAAA, that's the only setup the Lite supports) are closer to be flat this resonance becomes more recognizable: the frequency gets slower so the cycle of a single flick becomes slightly longer.
I don't see this with my stunt sabers so I guess this is a feature or side effect of the Lite board.
My guess would be that since there are multiple energy consumers in a saber with sound (the LEDs, the switch if it's lit and the speaker) that's how the power is distributed between the parts.
Since the stunts have only the LED, the power output towards it can be smooth and steady.
Again, it's really a tiny thing so don't get excited about it nor consider it as a pro or cono for a purchase
Hope this helps!