I disagree with the above comment about flat bars and long rides. Though a singular hand position certainly has the potential to cause discomfort over long rides... 1) 6 miles 1-way is probably not long enough to do you any harm at all, 2) 'fit' makes a bigger difference than multiple hand position options, 3) you can have just the same pain or nerve compression problems with multiple positions.
Agree with these comments. A flat-bar hybrid style bike works for this short commute. And the most important thing is how the two bikes feel when you ride them, is the fit good? Assuming you can test ride both bikes, take them out and see which one you like riding better and is the best fit for you. They are both similarly spec'd and priced, so it should come down to fit.