An incandescent has 10-15% brightness flicker at 120Hz. LEDs... vary. Some flicker a lot harder at 120Hz, some (mostly LED Christmas lights) are awful and flicker at 60Hz with a 50% duty cycle because they're a single diode rectifier.
Most LEDs flicker far faster, in the kHz range, which is theoretically beyond human impact, but we don't have many studies on it.
Incandescent flicker is also related to bulb wattage. A higher wattage bulb, with a thicker filament, will flicker less because it has more thermal inertia.
Filaments are slow to respond to alternating current. So they do wobble in brightness a bit, but they do not blink like an LED does, which fluctuates between 100% off and on.
