J4 is basically an updated 440, as J2.5 was an updated 330. Bigger lenses. J4 central tube is longer than the Redfield, gives you a bit more mounting flexibility. Would say that the Redfield is somewhat better optically, but doubt you would notice much difference except perhaps in marginal light conditions. I have a J4 on a Marlin 39A but don't think I have a Redfield any more to compare it with.