As far as the MX173 goes - there is a difference of one pheromone between MX172 and MX173 - both of which are based on MX102. They are 14 and 15 (respectively) pheromones in them. I do not know what pheromone is different but I would bet it is 'none based on your observations. I used MX173 (to go size) but do not remember why I liked one over the other.