Let Me Down may sound less inferior over I Forgive You. But releasing that single after DS can possibly plummet her sales. The haters and the casual listeners will then again label Kelly as a boy-basher artist and that she keeps on singing same type of songs over and over again. If IFY will be released even it if is outdated and sounded like a 2005ish track, the chances of getting consistent sales will be greater since it's radio-friendly and enjoyable to listen.
Releasing DS to radio is already a risky move much worse for LMD.