Washers are available in many different capacities and qualities. The type of cleaning you plan on doing will determine which unit is best for your application.

For the occasional washing of vehicles or other items around the home a very small high speed direct drive unit could be used. The performance and life expectancy of these units normally has a low priority.
For more demanding applications where the washer will be used more often and for longer periods such as car lots, etc. a direct drive moderate speed unit can provide performance with durability.
For the most demanding applications such as car/truck washes and heavy equipment washing a belt drive washer would be recommended.

In almost all cases, all types of washers are available with electric motors or gasoline/diesel engines and will be either a portable design or stationary mounted.