Are wood stoves with glass windows less efficient?

[squidy]

I mean it's okay if they're slightly less efficient, but are they significantly less efficient than an all-metal stove? A lot of the stoves I'm looking at have a window, and I kind of like how it looks, but I want a stove that will stay warm a long time after the fire goes out, (like to heat the house through the night) and it seems like these window ones would cool off faster than one without.
Also, does the size of the window make a significant difference? (Maybe I could get one with just a tiny window..)