I'm on the black box band wagon!!! If your boat is not naturally in the zone then you need something to get it there. The reasearch shows that the box reaches out and touches the fish for a whole lot further than 10'. Naturally any boat (aluminum or fiberglass) should be between .6 and .8 of a volt positive. For kings you need to be around .6 - .625 and for silvers .65 - .675. If your boat is naturally on the high end of the spectrum you will be repelling the fish. Now having said that when the fishing is hot like at Sekiu I don't thnk it makes much difference at all, but when it is scratch fishing every edge that you can get will make a difference. I think that it has made a difference for me. As for which box I think that the Pro-Troll is a Scotty with a different name on it. Hell we spend more than $200 bucks on gear a year so why not give it a shot??? Besides that we need to get more stuff...right ??
Good luck and tight lines, Jeff