It's a bit of comic bias, but Fort Max was just a taller than average bot in basically all but one (cameo) appearance in the various (Western) TF comics to this day. Whereas Metroplex has always been displayed as incredibly huge. [Maybe the toy should come with a reprint of #186/7?]

Giant Fort Max is a great toy but is best as a standalone display piece (or with his brothers) whereas a new giant Metroplex will look "right" displayed with classics.

I know Fort Max was giant in Rebirth but Metroplex was also huge and got a lot more cartoon screen time through season 3 and was more memorable for it IMHO.

I do agree though that Fort Max as the grail-worthy biggest Transformer is a title he should hang on to although Encore rerelease has dampened it a little. Even though Metroplex might be taller, Fort Max will always be the biggest G1 Transformer and a key piece in a G1 collection.