I've not used them side by side on the same car, but I could see them as being complimentary depending on the use case.
Recently I gave my youngest daughter's car one last good detailing before she moved out of state after graduating from college. Her Honda fit is starting to show signs of clear coat failure and the paint is already shockingly thin. This meant no claying because, as you noted, I'd have to then polish out the marring. The paint is too fragile, so that isn't really an option.
This car had sat for at least 6 months in an college apartment parking lot through all weather conditions and it was pretty grimy. In order to deep clean the paint as much as possible, I did a pre-soak with CarPro Lift. I was quite impressed by the level of cleaning this pre-soak performed. The clarity and feel of the paint was much better than I recalled from previous traditional bucket washes. A follow up with a bucket wash had the paint pretty looking pretty good.
A long story to say, I think a good pre-soak would get you 75% (purely subjective number) of the deep cleaning you'd get with a claybar, and it is likely "good enough" depending on the job and/or your standards. I don't think it will get the tough deeply embedded grime out of a clear coat like a clay bar can, but would eliminate a lot of the grime you see on the bar when you don't use them.