I've got the 8HP master blaster and the side kick... to be completely honest, I use the side kick way more. It is the perfect size to grab and use without needing to get anything setup. It works great for removing water from all of the cracks & crevices that it hides in such as door handles, mirrors, gas caps, panel gaps, etc.... and I also love using it to dry wheels and tires. It is a product I can't imagine living without after using it for so long.
Now if I want to dry the entire vehicle with air... the 8HP master blaster is clearly the better choice.
Both products, however, perform great for their intended purposes. They move a lot of air, are easy to use and the nozzle allows for easy control of airflow, and the rubber tips make it much safer to use around your delicate paint.