In my opinion, using either one is good, Krown or Rust Check, but nothing is as important as the application and the person doing it.
I was Rust Check for years then went with Krown as I heard/read it was slightly
better but the place I got it done did a shitty job imo as there were lots of dry spots on it when I brought it home.
About 5-6yrs ago now, I was told about a Rust Check place here in Oshawa on Bloor St and the guy was suppose to do an amazing job?
Long story short, I went to him and in all honesty, I could not do a better job myself, and I use to do my own.
When I took my Ram to Chris back in June, he spent 2hrs doing my truck and when I looked, I couldn't find a dry spot anywhere!
For those in the GTA or Durham region, I suggest you give Chris a call, you will not be disappointed. (Don't leave it as he gets booked up real fast)