I got the black because I had ordered an Alien LE in green trim, and I though that would be too much green in my small collection.
The black looks awesome, but for a long time I thought I'd made a mistake, and should have gotten the green. Now that my collection has grown, I find that the black sets the LE apart from the standard silver of everything else. Also, I picked up an RFM a while back, which has black trim as well. It actually gives them both a cool "family resemblance". That's a pretty specific reason that is completely irrelevant if your game isn't right next to it's younger brother.
In any case, you sure can't go wrong with Black, but the green sure is pretty.