That is a great question. I had used Fluke 77s for almost 20 years and upgraded to a 179 a year or two ago.
Biggest advantage: The 179 just seems nicer. I think it's a bit more accurate and has a few little extra features, but it just seems nicer.
I'm also testing a 115, which I plan to get for my technicians, who currently use Fluke 73s and Amprobe 37XRs. The 115 does everything they need and is a bit more compact.