A) Light Phidget has a much broader range for light measurement (much lower minimum and much higher maximum)
B) Light Phidget is a VINT product, meaning you'll need a HUB0000_0 to attach to it, where-as the Light Sensor 1000/70000 use any analog input port to measure it (1018/DAQ1000/etc). This also means it's somewhat intelligent and you can talk to it directly, detect if it's attached, things like that; the Light Sensor 1000/70000 are passive devices.