For cleaning my car:

I want one that's easy to change the attachments with. I have one now, and going from water-sprayer to soap-sprayer is very difficult - I've used a vise before!

And I'd like it to be convenient. Mine has no place to wind the hose, or electrical cable.

Last, a locking trigger, or very light trigger.

Should I get a gas one, to use with a foam lance?

Thanks!

Why you need pressure washer? Just to wash a car.
When I bought mine. I got the one that had the most pressure. That I had money to buy. I don't clean my cars with it though.

I went through this last year, but the reason wasn't for washing cars although I can use it for that. Anyway I landed on a Generac "prosumer" I think it's model 6564. Seems to work well and I hope I made the right choice for long term durability...I can't stand tools that don't hold up.

I went with a Honda 3600 psi