I used to work for Generac, I sold boat loads of these things to consumers and mostly professionals. Like anything, you get what you pay for. The key with a good washer is not the engine per say, it’s the quality of the pump. The better ones tend to be a Swedish made pump. I have a Generac that goes upto 3100 psi, it’s too much for household use. For sidewalks, fine, but you will force water in where you don’t want it on you house.
My advise, fine something that tops 2000psi, and I’d go Electric unless you need the gas portability. They cost less and fail more, but the honest truth is they do a damn good job and keep it simple.
The question to ask yourself is, WHEN the pump shits the bed, am I going to have it replaced for half the cost of the unit or am I going to buy a new one? If you are a replacement guy, go buy something with a Honda or Generac motor ( buy the Honda) and MAKE SURE, you can buy a replacement pump, so it better be a reputable name that will be around in 4 years when it dies.
Also, do not run cleaner through the soap hoses, regardless of it being there, it shortens the life of the pumps and it’s not worth it. Get a $10 garden sprayer for all the chemicals/ soap and use that as a pre treatment, then wash.