...the idea of rubbing dirt (regardless of how fine it might be) onto the paint makes the little hairs on the back of my neck (and everywhere else, ftm) stand straight up in rapt attention. Clay is an abrasive, and abrading the paint to 'clean' it can't be a good thing long term, regardless of short term results. I know, i'm old fashioned...
It is more like silly putty than an abrasive. Swirl remover has more abrasive in it than a clay bar does. Plus it is used with a lubricant, usually soap and water. It is labor intensive as the bar grabs fine particles embedded in the dimpling of the paint and you have to keep working the clay to make sure you are not using the particles you've drawing out of the paint as a fine sandpaper.
Think of it more like a lint roller to lift the debris that helps oxidize and discolor the paint away from the paint.
I'm pretty old fashioned myself. I painted my first car with lacquer paint, wet sanding between each coat. It was my first full car paint job, inside and out, and had only helped on car paint jobs before that one. Took for darn near ever to finish, but it looked great. The last step was to polish the paint, with an abrasive compound. (Not something you'd want to do with a clear coat finish.) It was a great paint job for such a crappy car.
My last vehicle was clay-barred, sealed with Zaino, and washed infrequently. Resealed even more infrequently. Parked in driveway or parking lots, or 99.9% of its life outside. Driven hard. It has over 309k and is almost 10 years old. The paint has no fading and looks good. (Any fading would be apparent as a deer caused the right fender to be replaced last year and stock factory color was applied.) Sure, the front of the left fender, behind three of the wheels, and grill have chips, but except for that, it looks great.
I may be crazy and too modern, but the results I have now will have me clay barring my Fiesta the day I get it. I'm too old and too busy to be repainting in my garage in the next 10 years and I don't know a paint man that I would trust that is not already retired.