I've used both. The eastwood is infinitely easier to use! The POR-15 requires a pretreatment and a lot of prep. When dried it forms a hard, shiny service that cannot be painted over unless scuff sanded. (This stuff is rock hard and doesn't sand easily!) There are also specific paints that can and cannot be used as a top coat.
Eastwood came in a 20 oz spray can, at least the stuff I used! That can held a lot of product!! Sprayed on, and best yet can be painted over the same as any convential primer. Throw the above mentioned test results into the mix and I am now a true eastwood convert!
NOTE: POR-15 is a great product, it is simply a pain in the butt to use compared to Eastwood's rust incapsulator.