I've been carrying both the F9 4i and the King Black 4U around this whole season so far and its official the F9 4i has replaced the 4U in the bag for the remainder of season. Nothing against the 4u but the F9 gives me about anther 20 yds of distance and an absolute weapon off the tee. I have been able to work it both directions when I've wanted (for the most part) and even on miss hits I get plenty of yardage with a mostly straight ball flight.
It leaves a little gap in my bag around 200-210 but I'm ok with that for now
When you say it leaves a gap, does that mean you now use the 4 iron as an approach club, in addition to off the tee? If so, what is your yardage with it for approach shots?