Commercial Solar Lighting
Solar lights that are in production for commercial applications such as roadways, billboards, parking lots, etc. have a higher up front cost but they will pay for themselves almost immediately. These systems provide lighting for specific applications with different clock settings. They also provide many days of stored power to provide continuous reliability.
The light power is different as well. Each system is built for the type and wattage lamp that will be utilized for that specific application. Lighting a billboard will take much more power then lighting a small pathway which is also different from roadway and parking lot applications. That makes the commercially manufactured solar lights more versatile.
Non-Commercial Solar Lighting
The solar lights you can purchase at your local home improvement store are much different. There is still battery storage, but it is small and only has enough power from the amount of sun it received that day. If there is a cloudy day, the lights will not last as long. For example, I have solar powered rope lights on my back patio. These lights will work from dusk to dawn all night as long as there is enough sun during the day. On rainy and cloudy days they turn off after about 5 hours or less. They also do not provide enough light to even read from; just a faint glow from the 20 LEDs in the rope.
If you are lighting up a driveway or walkway just for markers or environment lighting, these work perfect. If the project requires more lighting for security or large applications, commercially manufactured solar lights are the way to go.