Fire needs air to spread, the more air, the quicker the fire spreads.
The joint (pictured left) has more air pockets. This causes more airflow, allowing the ember to spread quicker. The Cannagar (pictured right) is compressed to form a perfect cigar shape, with one main source of airflow given by the skewer
When the flower is compressed as tight as possible, there’s less room for air to cause your weed to burn faster. You’ll get to fully enjoy every single gram of your flower.