The difference is the size of the unit, amount of oil it holds and the square feet it disperses to. The pro is much larger and holds up to 16 oz. of diffusing oil. It can disperse up to 4,000 sq. ft. and can also be installed into your HVAC.  The hose is included in the “Blondie Pro” for your HVAC installation.  The “Blondie Mini” is much smaller and easy to hide in your home.  It holds 4 oz. of oil and disperses up to 2,000 sq. ft. We designed this unit to make a powerful punch. It dispurses more scent than most battery or app enabled small units. It also covers 3 times the square footage than most small diffusers of its size.