The guides always seem to just advise the fastest one, but oftentimes the fastest one is the fastest because they won't do anything, IE:Cullen thinks it's ridiculous to support a Bard and so he takes an hour while the other 2 take three hours, but his yields no reward because he doesn't do anything. I think Morvan has arrived is another where Cullen poo poos the idea. Josephine can try to play it off politically but Tevinter sees through it, I just used Leiliana for my most recent one and so far it's worked, got some influence and Tevinter is none the wiser.