Ask HN: Stuck making a decision whether to hire

I have a contract-to-hire employee who has done satisfactory work for the past 3 months. I need to make a decision soon on whether or not to hire. I'm stuck on the decision.

This person has 6 years of experience. I would consider him a relatively average, mid-level developer. We have one other developer who is very good and experienced - along with me.

The average person has taken feedback well, has shown some improvement and is meeting the requirements. I haven't been impressed, but I also haven't been disappointed. When I ask him to do something, he does it but doesn't do much more. He seems to struggle without structure and predefined tasks.

PROS: He's very eager to learn, humble, has a great work ethic, picks up new technology fairly quickly, takes feedback very well.

CONS: Has grandiose ideas that are often irrelevant to the task at hand. Gets distracted easily. Has difficulty taking an abstract concept and breaking it down to actionable pieces.

Should I be hiring only A+, "rockstar", talent or is there a place for an average developer in a startup? Cost is not really an issue. How can I move past this point of indecision?