On an electric guitar, the construction of the body is of limited importance. At the high end of the market, people worry about the tonal qualities of various kinds of wood, but for the most part, we worry about an electric guitar body being as rigid as possible, and the pickups are where most of the character comes from.
On an acoustic guitar, the construction of the guitar itself has the most impact on its sound. You are hearing the vibration of the sound board, so what's important is the frequencies that are absorbed or reinforced by the way the body vibrates, and the way the bridge transmits vibration from the string to the body.
You can put great strings on a bad acoustic guitar, and it will still sound bad.
How do you know a guitar is good quality? Use your ears. If you can't hear the difference, the difference isn't important!
However, one rule of thumb is that plywood is the mark of a cheap guitar. You can recognise plywood by looking at the sound hole -- you can see the layers. You get a significant step up in tone from a solid wood sound board.