POR-15 VS Herculiner, anyone?

The floors in my Barracuda had a lot of surface rust so I used Por-15 on the whole floor of my Barracuda. I followed all the directions. Works good but after 7 years the drivers side floor has rusted out a little where it was pretty rusty. I didn't coat underneath the car, that's probably why. I also used Por-15 on the rusty hood of my van, and I did not top coat it. Within a year the sun had faded it and the hood was rustier than when I started! It was a big disaster.

I'm now using Master Series Silver Undercoat on the '69 Valiant and I like it a lot better. I'm not so sure about the colour, but you can paint over it easily, unlike Por-15. It's a lot smoother to paint, you can paint over it, it's not susceptible to damage from the sun like Por-15.