Die cast ain't the only thing I like about a toy. Hell, I don't understand why people like die cast anyway, if it's there it's there, if not who cares as long as the toy is good. Equating weight or just presence of die cast with quality is not always true.
At 31 cm, the 1/48 would be noticeably, not incrementally, taller than the SDF-1.
I would like to have both of these. At the moment, there is too little known about this figure for me to get excited about. I want to know more, then I will make my decision.
Besides there is only so much you can do with an SDF-1 Battlecruiser than a YF-19.