I don't think his chorus is that bad compared to the official Overdrive theme song. He can sing better too. It would have been nice if the song was used at least once in the entire season somewhere (maybe in a focus-episode about his character Will?). One of the reasons why I think Disney did not select his song is because of lyrics such as "Black ranger 'cause I'm black!" and "This ain't a program on Sci Fi!" Samuell Benta is the 2nd actor to be black and play a black ranger. Walter Emanuel Jones was the 1st with his role as Zack the Mighty Morphin Black Ranger. There was a controversy way back during the first season of Power Rangers about the black ranger being black and the yellow ranger being yellow (Asian). Disney probably didn't think of it much when they cast Benta as the Black Overdrive Ranger. The lyrics from his song probably brought it to their attention and thus, they figured that there was no way they could use Benta's song without creating a controversy. Hence, the final selection of another song. Either way, they are both rap songs that sound too terrible to be the official theme song of the Operation Overdrive season. Power Rangers has used mostly Rock songs in the past and it makes sense because the show is action-packed which goes really well with the high energy of Rock-style music.
You can listen to Benta's "Operation Overdrive" track below:
Operation Overdrive (Live version) at Power Morphicon 2007: