I have a portable pressure washer that’s just a petrol-driven moderately-powerful cold-water machine on a trolley. While it’s fine for the kind of work I want to do, you might be better off using something else.

Portable

Advantages: Because it’s portable the hose length shouldn't be as much of an issue that you need to worry about. Also cheaper.

Disadvantages: Doesn't look as professional as a well-presented trailer setup. If you want a portable hot petrol-driven machine it’s going to be difficult. I believe all-in-one petrol-driven portable hot pressure washers are only available in America. Oertzen do make a portable hotbox however that connects to your cold pressure washer, but it’s expensive.

Trailer

Advantages: Allows you to have a much more powerful, heavier, albeit expensive machine. If you intend to have a hot setup you'll probably need a trailer.

Disadvantages: Costs more to insure and setup, difficult to drive/reverse, takes up more space in a garage.

Combine the Two

You could have a trailer with a portable cold machine inside that you can hook up to a burner when the need arises.

Static

Say if you have a factory/restaurant/farm and just want your machine to operate in a single area because food preparation, or some other kind of messy work occurs there, you may choose to have a static machine.

Static machines can also be attached to walls.