I assume you mean solid v. multiple thin layers.

Talk to the person selling the instrument. Contrary to common belief it can be very difficult or often impossible to tell by sound.

It's generally assumed that a solid top sounds better than layers, but a well-build layered top sounds as good as anyone has a practical use for. For example, D'Angelico sells a $25,000 archtop with a layered top. I actually don't think any of their guitars have a solid guitar and they average $10-15k. They've lost one artist over it but there hasn't been a significant difference in sales since they switched from solid construction (when the founder died and they were bought by some Asian dude).