ywilfred
There's no difference between 780 and 740. I think (740 + Great Essay + Fantastic Resume + Excellent Interview) can easily beat a (780 + crappy essay + crappy resume + crappy interview [and there's even assuming you get an interview with a crappy eassy and resume])
Although I would agree with the second part (740 + great other stuff will beat 780 + crappy other stuff), I disagree that there is "no difference" between a 780 and 740.
Top schools want to keep their GMAT avg over 700, so taking a 780 allows them to take a non-typical applicant with a 620 rather than 660 GMAT. A very minor point however.
I would still suggest not retaking the GMAT unless you got under 40 in V or Q. Otherwise, work on those essays and getting a stellar application together.