A two pack of WST Leaders, possibly with recolouring to both figures to make them uniquely exclusive to the regular versions. It looks like Megatron has the blue legs instead of red, but I can't tell if there is anything different with Optimus.
Well, according to this link:
http://www.soundwavesoblivion.com/japanesewstf.html
Optimus has darker windows and Megatron does indeed have blue legs. I'd get it for the blue megatron (it represents the diaclone, goodbye Megatron, and Megaplex versions), but if you already have Optimus, this one with darker windows sounds a bit disappointing.