What is the advantage of using something like a BarFly mount to hang the front junction from vs using the stem?

cant think of an advantage to doing it that way. I can think of several disadvantages though.

Such as?

it's less exposed under the stem. less likely to get knocked around, or knocked off a mount. in fact, mounting under the stem even in a crash, as long as it's not a very severe crash, should keep it protected. less likely to accidentally bump it or hit the buttons.

I have mine mounted using the bottom of a Barfly 2.0, pretty much for aesthetics...just looks like a "cleaner install" in my opinion...doesn't make it any more or less functional and I've never had any problems.

See, I think mounting it further up makes it less aesthetically pleasing due to longer wires exposed and such. Do you have a pic of your install?

None of these show the wires running to the frame opening

It's just one wire running down to the internal junction box

Just moved mine to the Barfly, really like the way in cleans up the stem area.

do you like being so far forward on that bike?

It works for me, short femurs and a long torso.