I just looked up Flood Penetrol, and did some reading on some other websites about it, and they all refer to it as being added to paint to enhance the grip of the paint on the surface that you are painting. On the other hand, the Fluid Film is a lanolin based product that adheres to metal to give it a protective surface and to repel moisture. I see these two products as both adding great value in preserving metal, but also totally different uses. Possibly Flood Penetrol has another product that is similar to Fluid Film that I didn't find in my search?
The only negative thing that I have ever heard about Fluid Film, is that mechanics hate it, since it never dries, and they equate it to working on a car that has leaked oil and is covered in a dirty grime all over. To me, if it protects your car from rusting, it is worthwhile. Last night, driving home, the roads were salted so heavily, that in some places, you could see small piles of salt on the roadway. As a result, I have seen 4 & 5 year old cars that were so badly rusted, that they looked like they should be in the scrap yard instead of on the road.