The first thing to recognize when buying a decanter is that there is a difference between a wine decanter and a spirits decanter. The main difference is the result of the intended use for each.
Spirits decanters are more about appearances, and perhaps just hide less well thought of brands. For this reason, decanters tend to be more bottle shaped and ornate, with applied glass features and cut crystal.
Wine decanters on the other hand are generally used for aerating wine and allowing it to "breathe," which means exposing a greater surface area of the wine.