This was paper expands on our previous work that showed that there were opposite trends in the amount of exact exchange needed for Koopmans' ionization potential and accurate excitation energies. Here we show that this is due to the DFT delocalization error leading to a systematic underestimation of the computed IP: http://scitation.aip.org/content/aip/journal/jcp/142/18/10.1063/1.4920947