While the pump certainly is important, don't under estimate the importance of the engine. I tend to avoid the Briggs Inteks, cheaper Kohlers, and Chinese Honda clones. The Subarus I only see occasionally, they can be decent engines but the parts are very expensive and hard to find.
My point is that looking at it from the perspective of which part has the most potential to go bad first in a pressure washer, it has to be the pump.
In my own personal experience, I have owned four homeowner grade units:
1. A Craftsman with a Tecumseh motor in it. The Tecumseh ran flawlessly before and after the pump went.
2. A Campbell Hausfeld with a Briggs in it. The Briggs ran flawlessly before and after the pump went.
3. A Troy Bilt with a Briggs in it. The Briggs ran flawlessly before and after the pump went. (In the 12 years I had it, I did have to clean the carb once.)
4. The Costco special that I now have with the Subaru. No issues to date.
These units were prepped properly post use every time, including use of pump saver, and stored properly every time. Other than the carb cleaning on #2, there was never a issue with any of the motors involving any kind of repair or parts. Oil was changed on all units as needed.
#'s 1 and 2 were sold and were purchased for the motors. #3 is currently in my shed. It will probably eventually experience a similar outcome.
That's why I say that the pump is probably the most important consideration. IMO, it is the "Weak link." They are basically expendable. While I certainly appreciate a decent quality engine (and I am far from being a Briggs fanboi,) the motor in these units are more than likely going to outlast the pump. That's why I say that the motor should not really a huge, or sole, factor in these units.
In any piece of equipment that deals with transporting water (even if not at any pressure,) it's about the pump (and the quality of it.)