One thing I've often wondered is the difference, in the effect it has on the car's paint, between clay bars and, say, an all in one product like AG Super Resin Polish. The reason I say that is going right back to the days when I used Turtle Wax original - a product that contained cleaners and a protective element. Using a white cloth you would see clear evidence of dirt being removed on the applicator. Clearly the cleaners were removing contaminants.
Detailing clay is a relatively new concept. Going way back, my Dad used to use simonize polish and simonize wax. The polish did the cleaning bit, the wax the protection.
I think what I'm asking is this - do you really need to clay your car or isn't this just adding another step in the process? Not having a go at clay but we managed without it before and cars could still be got to a high state of shine.
Interested in arguments pro and con.