I was lucky and found an almost new Troy Bilt 2700 psi on Craigslist for $100. It does everything I need a washer to do. I purchased the quick disconnect kit from Lowes, which adapts inlet, outlet, garden hose, handle/wand to a QD.
I think most gas powered washers come with 4 tips of various size difference, the color coding is standard across brands.
I have a two story house, so when I wash the second story once a year or every other year, I rent an 18 foot extension from our local rental shop, $20 for the weekend, and its one less thing I have to store. I'm over 50 and would not want to hold the 18 foot extension for a living, but once a year isn't bad.
I had an electric I purchased in Home Depot about 10 years ago. It always seemed like more work to get out of the case, hook up cords and hose, and the pressure could not wash a house. It was like folding a map to it back in the case. With the gas powered, its so easy to start spraying, I don't think twice if I need to wash something. Just my two cents.
The little I know, washers are pumps with a gas engine. The pumps seem generic. The price difference is for the engine, Briggs, Predator, or a premium for a Honda.
If you are not in a hurry, they seem to come up often on Craigslist, people just get tired of washing the house themselves and don't have another use for it.