I love my pressure washer and prefer using it. I don't find the 2 minutes it takes to wheel out, hook up and pull start much of an inconvenience.
1. For lightly soiled or dirty vehicles, a pressure washer, foam cannon & blower can be a true "hands off" the paint wash. This is important for many as our dirty, aggressive and often too heavy hands are what I believe contributes to the vast majority of swirls and other love marks on the paint.
2. You can remove probably 90% of "swirl capable" particles on muddy, salty or otherwise extremely dirty vehicles before you even touch the paint. This again = less wash induced swirls.
3. Less water to dry if drying by hand
4. Just like steam cleaners reduce the need for chemicals on interiors (and exteriors), pressure washers do the same for exteriors.
5. They are just more fun to use
With all of that being said, it is also probably one of the most "novelty" detailing tools I use. It is not needed, and even though I use it on near every wash I still do a final "Flood Rinse" with an open hose. If your budget allows, and you have everything else you need, then it is a great tool.