Well i`d say there is no benefit it just looks posh.My brother gave me a  decanter made of Bohemian crystal and i only use it for old wines with a lot of tannin or for portwine on aspecial occasion like x-mas or easter or so.To leave a whisky in a decanter for a while standing in light and perhaps with a bad stopper can turn a whisky bad too quickly.With wine you don`t have that problem, that is mostly gone within a day with a dinner.But i agree it looks nice.