It kind of seems like you've already made up your mind here. If you think that you can get more value out of the job for the time being, don't feel bad about taking it.
I see the big variable that you haven't talked about here is your commitment level to this particular startup. Is it something that you love doing? Or is it just something you are passing time with.
In my experience, I've built startups that I could have jumped ship on. With others, that thought wouldn't have even entered my mind.
So I think the variables here are more than just should I take the job or not. We don't know your situation well enough. My guess is you are already leaning one way though.