Hobbies And Interests
12-Volt Lighting
Lights powered by 12 volts are likely to be a little brighter than 6-volt lights, because they use double the voltage to operate. However, the effect will not be that great. The filament inside a 6-volt lightbulb is thinner than that in a 12-volt bulb, meaning the brightness is similar. A 12-volt lightbulb circuit uses more electricity, but because the voltage and amperages are so low, it's hardly discernible. It's likely 12-volt lights are powered by a transformer because 12-volt batteries are hard to obtain.
6-Volt Lighting
Six-volt lighting is equally likely to be powered by a battery or a transformer. Most string lights, such as you use to decorate Christmas trees, use 6 volts. Six-volt lights probably use light emitting diodes (LEDs). LEDs are long lasting, energy efficient and convert the power they consume into light, rather than heat and light, which ordinary incandescent bulbs do.
Wiring
Both 12-volt and 6-volt lights are wired using a method known as parallel wiring. Parallel wiring means that if one bulb fails the rest stay on, so you know exactly which bulb to change. Additionally, parallel wiring means the voltage of all the bulbs in the circuit is the same as the power source, so you can have as many lights wired as you need without having to increase the power output.
Conclusion
Both types of lighting are similar in terms of the energy they consume and the time they last. Choose 12-volt lighting if you want a slightly brighter effect, but preferably choose LED lights, so you don't have to change the bulbs frequently. If one set of lights has a transformer and the other a battery, then choose the set with a transformer. They are just as safe and you don't have to worry about replacement batteries.