I am new in to the business and am in the process of researching equipment. Money is not too much of an issue, so I want to buy a machine that can handle about anything I will throw at it. I am going to be doing graffiti removal, house washing, new construction brick cleaning, decks, flat work, and house washing. I am looking at 2 hot water machines to mount on a trailer. One is a 3500 PSI / 5.6 GPM unit and the other is a 4000 PSI / 4.0 GPM unit. Which one should I get?