1) Eliminate the word career from your vocabulary. It's something invented by beaurocrats as a rationalization for being timid.
2) Ask your self "can I identify with this product?" Or, more importantly, are you OK with other people making the connection that you are about "Y"? Can you say: I am X and I built Y" with a resounding sense of pride. Would you feel comfortable being introduced on CNBC as Mr. "Y". If the answer is not "Yes!" with an exlamation point, then don't take the job.
What you should never do, however, is base your life decisions on your opinions on what an investment banker might think.
That's not only a bad way to live, but also a bad way to run a business. Be your own compass!