I'd suggest starting by posting the finished song to SoundCloud, then posting a link here so we can hear it. (Many people do not – and will not – use DropBox.)
Beyond that ... and in all fairness ... "how, exactly, is your larger request possibly to be satisfied?" This is your(!) song. You alone have creative control of it. You should solicit feedback from as many sources as possible, then individually consider what (i-f anything at all!) you wish to do in response to that feedback.
(Remember: "opinions are like <!!>s ... everybody has one, but you might not care to smell what comes out of it, and you don't have to.")
Once you decide upon "a particular goal that you wish ... for whatever reason it might be ... to accomplish," then (IMHO ...) it might be suitable to post a question here as to how to accomplish that goal using Logic or GarageBand.
- - - - -
"I wanna quit being a computer consultant and become a composer and arranger at age fifty-three."
LPX 10.2 on a so-so MacBook Pro. El Capitan.
Just south of Chattanooga, Tennessee, USA