2000PSI, cheapo / on sale / clearance works for me.
recently picked up a "dirt devil" pressure washer. works good enough. i do not need 3,000 plus PSI. to much PSI, and hit any sort of wood with a pencil led jolt of spray, and you can splinter the wood and tear it a part. when cleaning decks and like. set the nozzle to a wide spread pattern, and keep noozle 1 to a few inches away from wood decks. (depends on wood) and it does its job.
the 1500 PSI (cheapest) out there, can work, but the little extra PSI is fine enough for me.
gas powered vs electrical. any were i need to go, to use a pressure washer, needs water, meaning either garden faucet, or a well. both which should have electricity. i do not need another engine to take care of. and amount pressure washer sees it's use. not worth trying to deal with "old gas" and then carb getting gummed up.
if you needed to pump water out of a lake or stream, and haul water for animals. a gas pressure washer, would be something to consider.
as far as pressure, i do not want "high pressure" that begins tearing the paint off of a car or tractor.