The difference between a Nitrocellulose finish and a Polyurethane finish is cost (Nitrocellulose costs more), tone, and protection of the wood.

Nitrocellulose is a thin lacquer finish that bonds with the wood. This allows the wood to breathe, producing better tone. With age, the bond between the Nitrocellulose finish and the wood improves and stabilizes, and the tone improves (this is a major reason why vintage guitars tend to sound better than brand-new guitars). The downside is that Nitrocellulose wears off relatively easily and needs regular maintenance. We recommend using a polish specifically designed for Nitrocellulose finish.

A Polyurethane finish seals the wood in what is almost a plastic coating. It offers great protection of the wood, but does not allow the wood to breathe and does not bond as readily with the wood, thereby dampening the tone somewhat. However, it is a much more durable coating and requires less maintenance and care. A Polyurethane coat is much easier (and less expensive) to apply, as well.