Checked again, and there is absolutely no difference between the day
mode and the senso mode at night. Light is not also as bright as so
many say it is. I have a suspicion that the senso thing is not working
and it is not going into night mode with full brightness.
I have one and it acts the same way. The only difference I know of is that in daylight mode, when it's actually daylight, all 4 of the underside LEDs light up. In senso mode, only 2 of the LEDs light up regardless of conditions.
At night both settings switch to night mode, and light up just 2 of the underside LEDs.
Have a Phillips SafeRide light now, but it also has it's problems.