look i only said the comics were stopping
When this new Voyager Class Optimus Prime was first introduced to us, we didn't know he was going to be a super robot's torso in some new subline imprint called Combiner Wars. And so we were all sort of staring at him, scratching our heads, wondering what was up. New Optimus was lookin' kinda weird. Photography of him cleverly obscured the combined-robot crotch hanging off his back, and his limb connection points and super robot head were likewise obscured. Knowing that certain elements were being compromised to incorporate a torso mode, not to mention existing mostly to be the eingineering groundwork for another toy, made everything fall into place.
Combiner Wars Motormaster is a pretty damn extensive retool of Combiner Wars Optimus Prime. They look like they share a bunch of parts, but it's always fewer parts than you think. Yeah, from the thighs down, they're the same toy, but nearly everything from there up is new. I'm talking like nothing but the fists, the backs of the biceps, and some structural parts of the torso. The entire front of the cab on either is different, as are the arms and chest and heads. Functionally, they are the same toy, but their sculpt differs.
CW Prime is a beefy friggin' Optimus Prime. He's a little pinheaded, but that's partly due to his transformation -- his neck sits on a rotating panel that obscures his head in truck or torso mode, and there's not a lot of clearance for it otherwise. The super robot head hides inside his giant backpack. His chest windows are fake kibble, with the real truck windows placed on the backs of his arms. His legs transform like basically any Optimus Prime ever. Motormaster is the same except he gets different sculpted details other than fake chest windows.
Both these guys are meant to be the torso of a combined super robot, so some key joints ratchet very toughly. The hips in particular are very solid, and their ratcheting resting points are pretty far from each other, which makes the sculpted slant at the bottom of the toes feel silly. There's no ratcheting point that lines up with how his toes are sculpted against the ground.
Optimus gets two guns that combine into a larger gun and Motormaster gets a gun and a sword that combine into a larger sword. The combined weapons are intended for their combiner robot forms. In torso mode, you can keep their chest clamshell closed, or open it up to place Legends Class Blackjack (or his future retool, Rodimus) inside as armor.
Optimus Prime's a beefy Prime, very wide and boxy, which are traits we don't get in an Optimus Prime toy much anymore, so I like him for that. Most, if given a choice between the two, would choose Motormaster. Motormaster gets far, far fewer toys, and other than the obvious Optimus legs the base toy seems geared more towards Motormaster than Optimus.