Quoted from xTheBlackKnightx:
Three plastic translites do not equal one quality back glass.
At Expo George and Gary specifically pointed out that they choose their LCD size so that the backbox art would still be there and be prominent. They said backbox art is an important part of pinball history that they didn't want to lose it like Heighway and JJP have done with their full LCD backbox designs. Its too bad Stern didn't take it a step farther and decide to use a real mirrored backglass as well. Especially considering the price of the SLE.
I also thought at expo someone said the SLE would get three translites shown plus a 4'th unique one. If that's true than I guess there's a chance that could end up being an old school mirrored backglass?