I have used both on my Lurcher, the DAP diffuser (plug in) did make a slight difference but not enough to justify running one permanently, Serene-UM, I have used for over a year and the effects are good at the beginning then seem to wear off, I am now trying a new product called Zyklene (also natural like serene-UM) cheapest place to buy it is www.vetuk.co.uk but you have to buy in bulk to make it cost effective and it IS good, dog is more confident, playful and less fearful I would recommend it. Going to try the Tellington TTouch next, Oz