this is a tough one. I have a couple of my first amp i built with f&t. later I got a great deal on the black JJ's. tone wise you would have to be very very trained to hear a diff BUT I keep going back to the first two I built with F&T's as a reference because they stand out tone wise. Could be a lot of things but...??/ if you can get them for the same as the jjs, then go f&t
kind of round a bout but hope the input helps a little.