What's the difference between the Single Wall and Double Wall?

Remark Inc

"What is the difference between Single and Double Wall?""Which one is better?""Does it sound different?" "But which one should I get?"  Stainless Single, Stainless Double, Burnt Single, and Burnt Double. It's easy to tell the difference between Stainless and Burnt, but what's the difference between single wall and the double...