Passionate people are intense, self-motivating, extremely energetic, and generally positive.  Hire someone who is passionate about what they do and your project will be better for it.  

Don't settle for average.  People with passion don't settle for average or merely acceptable.  They learn, continually and incrementally, from experience and actively apply that experience to provide the best possible solution(s).

Passionate people are not the norm.  They are not easy to find.  Remember that when you select a professional at random to work with, chances are, you will be selecting the average (or worse).  That's simply how statistics and probability work.  Do you want average?  No.  

Seek out the passionate person.  While a professional's qualifications are not to be ignored, you need to get to know the person you are about to hire.  You will be spending a great deal of time with them.  Make sure you understand how they work.  Get to know their process.  Ask questions.  Meet with them on several occasions.  Ask them to review a prior project.  Ask them to discuss the resolution of a problem they recently had.  (No problems, move on.  Everyone has problems.  Design and construction is complicated and problems will arise.  How they are resolved is key).

During your conversation(s), you will get a feeling for the professional's personality.  If they are passionate about what they do, they will enjoy discussing projects with you (both theirs and yours) and taking the time to do so.  It is usually difficult to get a passionate person to stop talking about their work.  

Is passion the end-all?  Is it free from defect?  No.  Passionate people tend to be strong willed, stubborn, and reluctant to back down from their position.  

However, complement it with open-minded and you have the magic formula.  You do need the professional to listen to you and hear what you are saying.  Many people listen, but many do not hear.  During that conversation you have with this professional, when you ask a question(s), do you get an answer(s)?  Do you get an answer you understand?  

Listen to what the professional has to say.  If you don't understand what they are talking about and they don't take the time to educate you or explain, move on.  If they make sense, you like what you hear, they listen and hear you, and are passionate about what they do, you may have found someone worth consideration.