Roger,
Don't get the wrong idea I think they are both good system's.I have heard good thing's about both on the board's that's why I chose the gibson in the first place. Next time I would try something different . Either back to flowmaster's or try a ravin system.(Just to get a little more sound from it.)
By that time my mind will change a hundred time's.Don't worry about it,just look at all the option's & go from there.