The mono to stereo on Youtube must be a default setting.
Agree that the mono - stereo difference is tiny when used the way I did. But film a truck coming out of the distance from the left, driving right past you and then disappearing to the right and the stereo effect is really cool. I'm guessing the stereo is also really useful if recording eg. chamber music. You'll be able to hear the violins off to the left and the cellos off to the right. The two little Azden stereo mics are oriented at 120° from each other.
I'll bring the Azden next time I'm in the shop if you want to give it a spin. By nature, I expect the large diaphragm mics you use would sound better because they are just that, large. But if someone wants to buy just one, as I did, then this quite small, mono-stereo Azden which can also sit on my camera's hot shoe is about as versatile as it gets.
Just a heads up- The Canon 90D ships in Sept 2019. They always get just a little better with each model. I probably couldn't do without AF lenses most of the time. I have a few. Just picked up a wide angle that is not AF because it was 2/3 less. When not using AF you need to know how to set it.
I tried lots of stuff for video. I have a C920 and I will say it is very convenient compared to capturing and transferring to a computer. Mine wasn't the best video quality though. Ok but not great. Next I had an old Samsung I bought awhile back 34x optical H.264...it's also just "ok". Highest rez is 720p.
I am using my wife's old DLSR right now. It's a Canon 70D. I bought a mic for the shoe on it. The AF in it works VERY well. The on board mics aren't bad.Probably not good enough to demo new violins to customers though.I have a Tascam DR-40 I picked up on ebay. The mics in the Canon are stereo and sound pretty good for violin.
Seriously considering the Canon 90D now since I have a fairly substantial lens collection for Cannon, I'll probably stay in that universe.
If i were really getting serious for video I would be shopping the Panasonic Lumix GH5s. They just announced it last week. I could be wrong about that model number but it's a brand new release. The thing about that one though is you need a lot of extras to really have a pro set up.I'm talking cinematic here....probably overkill for most of us. You can use it right out of the box if you don't want to go all fancy.
Looked at a bunch of info on mirrored .vs mirrorless. One video makes a visual comparison. For the average Joe, you probably can't tell the difference. Bigger for me is shooting in RAW .vs .jpg.