It's no secret, the formula for a decent sounding acoustic is:
Rosewood Back and sides and Spruce.
The tone created by these woods are naturally pleasing to the human ear. Every brand has a model with these specs so there are the finer points. Ultimately I myself look for the guitar with the most tone. Depending on the thickness of the wood, (which is rarely, if ever specified) the tone can change. If the wood is thinner, there's is usually more volume. The trade off though is detail. More mass of wood generates more sound from the wood so you end up with a more balanced and broader tone veriety. Most people pick the brighter, louder guitar because it's more exciting. I find the thinner guitars Choke out some notes and don't sound good past 7th fret. Sometimes the weight can tell you if there is more mass of wood but that can be veiled by the amount of laquer used or the weight of the neck.
It's best to use your ears. It's easy to strum a Mahogany guitar and a Rosewood and hear the difference. I'd say 90% of the people prefer the Rosewood instinctively. Pick the one you like.
I recommend trying a Yamaha L Series. The LL6 Tinted guitars always sound as good as guitars twice their price. You be the judge though.