Personally I like the translucency of the acrylic for a space theme. I am thinking of the feel I get from the colored die in Quantum, it just adds a nice touch.
Agreed. Thematically the MDF doesn't feel right. Even painted I think it wouldn't have the same effect as the acrylic.
On a personal note, I've never been a fan of MDF pieces. They seem... cheap (truth be told, they are generally a cheaper option).