The motion sensor needs to be hot 24x7.
Motion sensors actually calibrate for the environment, and if you constantly sever power to them, they constantly are reset and have to start calibrating all over again. The sensor won't tell you this, the only symptom will be poor performance, which you will misattribute to a lousy or defective sensor.
If you also need a switch, put it downline of the motion sensor. So that the motion sensor always gets always-hot and neutral.
Switch it to DC. Low voltage DC motion sensors are cheaper.
About half the inherent cost in an AC motion sensor is the parts to make low voltage out of mains power, and to switch mains power safely. Therefore low voltage DC motion sensors are much cheaper.
AC low voltage lights don't care if they're DC. But low voltage DC motion sensors do. So do LEDs and it's time to switch to those, now that choices are available that give good quality light.