@ TCampbell- Non of your new arguments/statements support the deficiencies of your original post. You have said nothing regarding DOF and high ISO IQ in your follow-up posts. I agree with Microbois that it seems you are changing your points in order to continue to argue.
"Removing the reflex mirror from the camera doesn't automatically make it a better camera."
Very true. But nobody in this thread claimed removing a mirror made a better camera.
"Image quality is primarily about:
1) Photographer skill (so that would be equal regardless of which camera they have)"
No argument from me on that point.
"2) Lighting (so now you probably need a camera that can deal with off-camera lighting and the smaller milc cameras don't do that, but many mid-range do and the higher-end models do. The camera needs a hot-shoe.)"
The OP never mention an off-camera lighting requirement. So far, I've purchased 11 mirrorless cameras, Panasonic, Olympus and Fuji. Each and every camera had a hot-shoe. Mirrorless cameras in the OP's price range have hot-shoes.
Have you ever owned or even operated a Mirrorless Interchangeable Lens Camera (MILC) for a significant number of images?
"3) Lenses (the lens selection for a DSLR are massive... both Canon and Nikon offer around 75 choices each... and then there's the third party lens choices from Sigma, Tamron, Tokina, etc. etc.)"
Yes, there are more native lens options for dSLR's than any other system. But:
A) How many lenses does one actually need? The OP mentioned that for starters all he was looking for was a stock lens (which probably means a kit lens).
B) Quite a few third parties are now making lenses for MFT, Fuji and Sony mirrorless. Including Sigma, Zeiss, Rokinon et al. I recently tested a HandelVision 40mm f/.95 for B&H which was designed with a Fuji mount. and
C) Most MILC (MFT, Sony, Fuji) have adapters available. These adapters allow owners of MILC camera to shoot lenses with Nikon mounts, Canon mounts, Leica mounts, Contax mounts, Sony Mounts, Pentax mounts, et cetera. So in actually, most MILC's have far more lens choices available than dSLRs.
Have you ever owned or even operated a Mirrorless Interchangeable Lens Camera (MILC) for a significant number of images?
"4) Camera body (and mostly it's the sensor -- size and ISO performance, etc. Other features are situationally important depending on type of photography such as focus system, shooting speed, etc.)"
Wellll ... and again ... that isn't necessarily true. In modern digital cameras, size of enlargement may be more significant than sensor size. The size of the final image is what typically dictates sensor size requirements.
"Nobody else has the OEM and 3rd part support for compatible products that Canon & Nikon have. That's a big reason why it's unusual to find serious photographers shooting with anything else. "
I agree that Canon and Nikon have more 3rd part support for compatible products. But the OP didn't request information regard 3rd party hardware. The Op is looking to purchase a camera and w stock/kit lens.
How do you know that 3rd party compatible hardware is why serious photographers buy Canon and Nikon? Cite your sources. Having been a professional, I say that 3rd party support is one of the last things that will drive me to choose a particular camera. But, once again, the OP is not asking about 3rd party camera hardware information for a serious photographer. Personally, I think that a big reason most serious photographers are shooting Canon and Nikon is because they are already locked into their existing camera systems and find it a financial hardship to switch to a different system which doesn't significantly improve their existing image IQ.
"If a person is starting to get serious about photography then they want a camera that can support off-camera lighting (it needs a hot-shoe) and they want a camera with a viewfinder (EVF of optical) -- not just the LCD. You can get both of those features in milc cameras (mostly in mid-range and up)."
I believe that most MILC's support off camera flash. I believe most MILC within the OP's price range have/support EVF's. In fact my Fuji's have, built-in, both an EVF and an OVF.
Have you ever owned or even operated a Mirrorless Interchangeable Lens Camera (MILC) for a significant number of images?