There is nothing a 4 string bass can do that a 5 string cannot, and there is a lot a 5 string can do that a 4 string cannot. Like playing a fretted low E, Eb, D, Db, C, and open low B, and playing more of the notes of a scale vertically, without changing positions. It's a no brainer. And this is from a guy who learned on a 4 string when 5 string electric basses did not exist. Go 5 string.