I have heard that PhD programs in 'Interdisciplinary Studies' specifically are not competitive. However, my potential main supervisor said that SPT and Com/Cult are both more specific, whilst being interdisciplinary, and are therefore more hireable. I have also heard that it depends what field and types of courses you want to teach one day. For instance, Com/Cult grads get hired in communications, information studies, cultural studies, etc., while SPT grad would get hired in another (and crossover) range of interdisciplinary programs or discipline-specific departments. So it really depends, from what I understand, as well as how you market yourself. Further, I have also heard that it really depends to what extent you are able to or are interested in relocating, such as away from the GTA, let alone Ontario as a whole.