I have a cheapie I occasionally use on the boat. As others mentioned, stay away from a straight tip, or something like a beehive which uses a straight tip that rotates at speed to achieve a broader pattern. You want a true FAN of water so that the ultimate power is diminished. That's why I like the cheapy unit as it will shoot water at a distance (and soap) but actually does not bring a ton of pressure to bear. You can use a bit more pressure on the nonskid, but I can't describe in email how much pressure is okay and what is too much.
Also, realize that waxed surfaces can become unwaxed if you use excessive pressure. Still, on a 48 foot boat, the pressure washer and ability to spray soap saves time. I like the increased ability to drive the silt down the decks that builds up in the nonskid areas, which I have a lot of.