I'd get the Merc. Even if you don't collect them chances are AA won't have them in future 1/18 models and only $$$$ 1/12 so you're sitting on a good resale value.
I have a standard black bookshelf with plain acrylic display case.
Should I tape up some LED strips on the backboard or just buy these?
Strips will be cheaper. Case will not necessarily be cleaner because I still have to find a way for the USB to plug into the wall. Probably brighter though because it's directed onto the model instead of coming off the back. The adjustable light posts doesn't look very clean though?