Dialogical is to have qualities that are similar or near dialogue. Dialogic is to be like dialogue. Dialogical is related to or to be of like dialogue. Dialogic is to have the form or to be an instance of dialogue. This structure is like the use in Turner of liminoid and liminal; but where the liminal, in spite of the technicality of the word meaning related to limina, is the closer, deeper liminality than the liminoid which is to have the appearance or form of the liminal. (I suspect that Turner was stuck with developing the term liminoid, where liminal would have been technically better, due to the already existing use of the term liminal. He thus needed to find a term which was further from the limina than liminal in meaning.) To put this another way, the dialogical is like a simile where dialogic is the metaphor for dialogue.