The Makuros was already pretty good in terms of quality, but the Diabolus just blows it out of the water. Crisp tampo, great paint apps, tight joints, ratchets where appropriate, ingenious engineering in the eyebrows/jaw, lots of customization/play options in terms of gun layout, LOTS of diecast (this thing is HEAVY. It probably has one of the highest weight to size ratios I have experienced on a toy), a light up gimmick, and overall a really pleasing mold design with loads of surface mechanical detail. Plus it comes with a chibi Megatron.
It's so good I'm considering getting another.