There is a very big difference between the two types of machines. The steam cleaner operates at a low water volume typically 80 to 150 GPH (gallon per hour) and the pressure is created by super heating the water well past the 212 degree boiling point, after that the water becomes vapor inside the machine usually at a peak temperature of about 325 degrees. The pressure created by the expansion of the water is usually about 80 to 150 PSI (pounds per square inch). When the vapor exits the machine it quickly cools into droplets of water making a hissing crashing sound. Like cold water hitting a hot frying pan, the super hot vapor hits the much cooler air outside and flashes into droplets of hot water. Steam cleaners because of their low water volume and pressure are excellent for cleaning greasy engines but don’t work for big jobs. Pressure washers use a higher pressure usually 1000 to 4000 PSI on most production models. Water volume is much higher usually 180 to 360 GPH. Maximum water te