Any metal surface will feel cooler than a cloth one, even if it is the same temp. I sometimes wonder if the belief the aluminum interiors are colder or warmer than the mouse fur ones is "conventional wisdom". Does one feel different because of a perception that is not objective? Has it been measured with a thermometer? Just curious since we're not going to sell ours with aluminum interior. If the windows are smaller (see Post #6) in the mouse fur units, that would probably make the biggest difference in temp.
We liked the aluminum interior—after all, isn't this about design and aluminum? We were concerned about the mouse fur (if you own one with mouse fur, you'll call it "lined") absorbing cooking odors plus keeping it clean. The aluminum looks really cool, especially when the lights reflect off it. Do not rub against the aluminum anytime, but especially in the winter, while naked—it will always feel cold. Maybe some people like rubbing against it, don't let me stop you.
So, like 28totow writes, it's a matter of taste. Make sure of what you like and then buy it.