Two finger power chords sound very energetic and fast, so they are great for fast passages. Three finger power chords sound a lot fatter and powerful, so they are great when you want the song to sound a lot more brutal (\m/) or more primarily when you want the power chord to ring out.
What fingers are used for power chords?
The power chord is the easiest and therefore most common chord in rock music. It requires three fingers; your first, third, and fourth. Your first finger is what denotes the root note of the chord you are playing. The root note is what gives your chord its name.
Is a power chord 2 or 3 notes?
Power chords are often used in rock music, and are also known as fifth chords. They're called fifth chords because they're made from the root note and the fifth. They're beefy, often crunchy and are super simple to play because it takes only three notes to make these types of guitar chords.