I noticed that there are two different circuit test lights out that are common. One says "low voltage" and the other says "Power On" What type of tester should I purchase to trace shorts and test wires? What are the differences between the two and how should I use each?

Get a multi-meter. You can do AC or DC, ohms, resistance, low voltage, high voltage, etc. Then you don't need a bunch of different meters....you got it all covered.

I actually have one but think a test light sometimes would be easier. I was just wondering if anyone knew the difference between the two.