OK, so another thread reminded me to update this.
After some disappointment in the way Krown's product seems to quick wear off of the underside of the car I experimented a bit with the Rust Check product....Rust Check actually has two formulas; the thinner (red) formula for inner panels, underhood, etc and a thicker formula for the underside. I bought a couple aerosol cans of the thicker stuff and touched up the underside of the DTS, then drove it in some big rain storms. Checked underneath and the Rust Check product is still coating well everywhere I sprayed it.
That experiment prompted me to take the Escalade for it's annual treatment at my local Rust Check facility vs. the Krown. Same pricing (too much IMO, especially with the 'large SUV' tax), but I would say that the Rust Check application was much more thorough, especially when it comes to the underside. After the application I checked underneath and it was thoroughly coated with the thicker product, and all the doors, rockers, etc were dripping heavily with the red thinner product.
Since the underside gets a thicker product, it drips less, but smokes more for longer than Krown. Mrs.Firm drove the truck in yesterday's rain storm, i checked underneath when I got home and the coating still looks as fresh as when it was applied, so I believe this is going to last much longer than Krown's protection.
So, my non-scientific approach to this suggests that the Rust Check product is superior, results obviously will vary by applicator, but I will be using Rust Check going forward.