perfect keyword domain, question??

Hi, I have read the fatcat guide and thought the part about domains was very interesting. I am promoting a trade type website and would like to know whats better in googles eyes.

Say my keyword is "boston plumber"

Which would be better?

bostonSplubmerDOTcom OR topbostonplumberDOTcom


I think the first would be great, but does the s in between the keywords hurt me? Please advise, I'm literly trying to do a perfect combo of whitehat and blackhat on this project and dont want to get to far into it without the perfect domain. Thank you so much! -Stereo