Back of the legs, the crane and the crane base (which encases the head).
The additional bulk around the head would be for that reason, but not the additional bulk on the legs. The crane arm is simply a bulkier piece than a ladder, and that additional mass needs to go somewhere in robot mode. Much like the hip panels on MP Ironhide/Ratchet, this is essentially vehicle mode kibble which has been displaced to a more discreet part of the robot body to make the overall look more cartoon-accurate. By placing it on the back of the legs it means that the rest of the toy will look more toon-accurate.
Agreed. MP Grapple does enjoy having additional lines on the shins which Inferno lacks, but that's purely because Grapple's cartoon model happened to have those lines which Inferno never did. So that part of Grapple incidentally enjoys a bit more extra detail. But I totally agree with your sentiment about MPs cherry picking the best of both worlds from toy and cartoon likeness instead of being so slavishly cartoon-accurate. Cos I'd imagine that a toy-toon hybrid designed MP Inferno would look more like this. The core engineer/design would be the same as what we already have now, but that additional detail on the sculpting would've been just absolutely gorgeous. But I suspect that we're in a minority here. The majority of fans have been crying for cartoon-accuracy for years and TakaraTOMY is giving them exactly what they want. So I can't really fault them for doing it.
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