C-level role at startup vs. middle mgmt role at large firm [closed]

I've wrestled with the same thing. Big fish in a little pond or medium fish in a bigger pond. Generally, I think it depends on what kind of steps you think best serve your career, and only you can know that. Considerations/questions:

• Networking: Consider your peer group. In my experience, while sometimes you'll be taken less seriously coming from a smaller firm, you'll be rubbing shoulders with C levels as peers, and that changes the conversation and it changes your sphere of influence. You'll be trading ideas and networking with Cs of smaller and larger firms.
• Career Positioning: Good and bad, being at the top of the firm positions you more as a senior leader and less as a worker bee. It's easy to lose touch with the actual work; even more, sometimes you HAVE to step away from the actual work in order to be effective in your leadership role. You can always step back into the trenches, but it's a little harder to do that. This seems like picking nits, except...
• You mention scope. I'd suggest that the scope between the positions seems equivalent in some ways. One firm has a narrow product scope, but you'll have broad and significant organizational scope. The other firm has a broad product scope, but you'll have a narrow organizational scope. I have no idea if these offset, but this move right here is positioning you advantageously for future positions with a broad organizational scope OR future positions with a broad product scope. You need to decide which is sexier for you. Which is to say....
• What ladder do you want to climb? Do you want to hop every 5 years or so to the top of progressively larger firms? Do you want to hop every couple years to progressively more senior positions within one (or several) big firms? OR do you want to grow your career by growing your company? Which brings me to....
• How much agency is important to you? How do you find satisfaction? There's a lot to be said for being in control of your work and your product and making a large difference for a smaller organization. It's fun. It's also exhausting and you lose the safety net you have, even if we're just talking about scheduling and freedom, that you'd have as part of a larger team. Finally...
• What is your best path to growth? Weigh the growth potential of the small firm with the upward mobility potential of the larger firm.

Good luck! Sounds like you don't really have a bad option, which is an enviable place to be.