its half the price and less than half the features. It all depends what you're trying to do. Making big power is definitely possible with a PFC, but personally I'd trust a fill standalone more in the long run.
Its not even that much more expensive when you consider how much you can make selling off your stock ecu, wiring harness, and stock sensors. If you're doing a proper 400-500hp build anyway, the extra $500 dollars for a full standalone (E8 is way cheaper than electromotive and still very good) isn't going to break the bank.