You can have your opinions, but don't let them cloud your judgement.
Ha! I almost fell out of my chair laughing at this. Pot, meet kettle. You're the one going around saying "Canon is the best manufacturer" and "Ken gives the best reviews" and the SR1 "will do everything you would ever need it to do".
To which my approach has been from the beginning that there's a lot of great stuff out there, no one camera setup is going to be the hands-down favorite, etc.
Getting back into the specifics,
No DSLR is smaller and lighter than the SL1 (you said so in your response the D3400 is lighter - but not smaller - and the D5500 and D5600 are still bigger - and heavier - than the SL1). These are the facts that you provided.
But it isn't. That isn't an opinion, it's fact. At best you are arguing that it's the smallest DSLR (but not the lightest), which is different. And then you stick a 18-135mm on the front, making it far from the lightest OR smallest option.
At best you are arguing for the smallest SLR
body, but not the lightest. As I said, I think if small size is a premium you've got better options.
GPS info can be added in post if you care about it.
It can, but that's another step in your workflow. Like I said, I thought it was a gimmick at first, but now its invaluable to me for archiving.
Mirrorless cameras are cool little gimmicks to me. The sensors are inferior to same-gen DSLR sensors. This isn't opinion (or bluster) - it's physics. Small physical sensor size with relatively high megapixel ratings equals poorer low-light performance. This is fact.
Hmm - maybe you should take a closer look; the sensors aren't smaller, ergo the pixel pitch is the same. In many cases the underlying sensor design is the same damn thing. Also worth noting that of all the top camera sensors being tested by labs like DxO mirrorless constitute roughly half of the top spots in any category. you are right that physics plays into it, but not in the way you suggested. The lack of a mirror box allows the sensor to sit closer to lens (i.e. a shorter flange distance) which changes the ultimate design of the lens. DSLRs like the SL1 rely on phase detection focus, which has its advantages and disadvantages
You are right about the image quality of the 18-135 lens - it's not nearly as good as more expensive lenses. But remember: the OP isn't looking to drop $3k on lenses at this point. The 18-135 will be all she needs for quite a while as she learns more about photography.
It's also not as good as equivalently prices lenses with less reach, and its bigger than it could be, particularly on a body you selected based primarily on its small size (see above). It still puzzles me why you'd select this particular combo. I'ts a pretty slow lens (I noticed you erroneously cited low-light performance as a dig against mirrorless) As for the learning about photography argument, I'm of the opinion that carrying a wide-to-zoom walkabout is more of a hinderance than a help for learning ... yes, that's clearly my opinion.
You are right that you might not like Ken Rockwell.
I'm not even sure how one can be "right" about something like this.
To be clear, I've followed Ken for years. He's a wealth of information, particularly with older 'legacy' lenses and systens. He also talks a lot of hyperbole and holds strong opinions, some of which goes far beyond the actual science, and sometime he is downright trolling for clicks and exposure. I disagree that he avoids hype and marketing. I'm not saying he's bad, I'm objecting to him being held up as "the best".
The video is 1080p at 30 or 24 fps - this is more than adequate for almost everyone (24 fps is what you see in theatres). 4k is overrated (I have a 70" 4K TV at home, and unless I sit within 8 ft, the pixel count is imperceptible to human eyes).
I could have been clearer. IIR (it's been a while) what I really didn't like about the SL1's video was the focusing, which made it almost useless on filming moving subjects. Regarding HD vs 4k - the advantage for me is that I can crop 4k, and pull usable stills out when necessary. 1080p doesn't give you that latitude.
I hope you were able to learn something from me, and I hope to learn something from you.
I hope the same. As I said, I enjoy discussing these things, and my antenna go up whenever phrases like 'the best' get brandied about. I'm naturally suspicious about any such claims. I remember when the SL1/SL2 came out and
personally I found so much I didn't like about it that I can't recommend it to the OP. Canon's focus at the time was to make the smallest, lightest DSLR they could, but to do this they made compromises (and the end result doesn't fit well in my big meaty hands). If you are going to carry around a big walkabout lens anyway I'd favor a body with a much deeper grip.
But yes, it, along with almost all other modern DSLRs, can be used to take excellent photos.