I have thousands of hours on the F75 platform, most recently the F75+. All in all it is better in all regards except trash ID for me, and in recognizing trash after 50 hours on the Legend it's equal or a slight nod to the Legend....after thousands of hours I was just in tune with the F75 and ID'ing trash but for a new user I'd say the Legend does better off the line. I also didn't have any EMI issues with the F75+, so it's pretty equal to me in terms of handling EMI. The Legend is deeper and much faster recovery. The F75 can hang in terms of depth in boost mode, but since I don't ever hunt in boost I don't personally count that. I still prefer the 1-100 ID range, so the Legend's compressed is taking some getting used to. One other area where the Legend excels over the F75 by far is falsing in heavy iron, and it's not even close....the Legend has a big advantage there.
I ended up putting my F75 for sale, it pains me as it's been really good to me and paid for itself so many times over with dirt gold I lost count, but I just didn't see myself using it much anymore. I'll probably regret this decision though.