I agree with Gary in that,
With 100ms I definitely can see some offset in the light vs the beats, 50ms solved the issue, but the problem was the fading in or out, a 400ms fading in 100ms intervals are just 4 steps (0, 85, 170, 255) where you won’t see a very smooth transition, in 25ms intervals are 16 steps (0, 16, 32, 48….etc) and the effect looks much smoother specially for LEDs which are much faster than incandescent lights.
I use 25ms in all songs since I use a lot of fast fading-out (100ms fading).