Well, I can tell you that the lighting level is higher than London--perhaps not by much, but it is higher. London, Belgium and Sweden all used the same fixtures, but newer, brighter ones were installed for Madrid. The items are more evenly lit and the general ambient light is higher.
Lucasfilm tries to adhere to a museum standard for the objects. The light can be bright but not hot on the objects, as even a moderate heat over three months could introduce warpage and damage. Hence, the objects tend to be lit darkly, partially in deference to the object's well-being and partially for an artistic look.
The displays here look great. Would be awesome if there was a permanent museum in the U.S. to visit. Wish MY photos came out this good back when I saw MOM when it started its tour.