I used the POR 15 on my second tank. You have to do all three steps at one time so its a little more involved. If you don't seal it up right after the treatment it will flash rust and it happens quick. The final sealer was easier to apply than the Caswell. It was thinner and easier to get into all the nooks and crannies.
Both sealers work. Despite all the steps of the POR 15 I prefer the silver lining appoased to the clear of the Caswell.