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Some pairings feel inevitable. "Friends" had Ross and Rachel. "The Office" had Jim and Pam. Elon Musk has SpaceX and Tesla.

But a deal between Musk's two giant companies could end up looking more like Frankenstein's monster than a Hollywood love story. And investors might struggle to understand and value it.

The SpaceX-Tesla tie-up isn't a shoo-in, but both sides are officially considering it . That raises questions about what's gained from a merger.

Combining the companies turns Musk's two jobs into one. Their somewhat overlapping AI plans could create significant efficiencies in areas like compute and talent. Joe Ciolli, author of the First Trade newsletter , broke down the pros and cons for SpaceX and Tesla investors .

These companies have A LOT under their hoods, though.…