In a good lighting condition, even a pinhall camera will take a decent photo. When things are not so optimal, which is more common than that, you need the "help" from a good camera to make up for your mistakes and technical flaws.
DSLR market is surely shrinking but I believe it's here to stay. Surely, mirrorless cameras with smaller sensors (than full-frame sensors) are getting better each year. So are full frame sensors. When the quality matters the most, stupidly expensive DSLRs with damn heavy lens will get you the best results (assuming the photographer knows what he's doing). Just like what happened to SACD, those who need the absolute best isn't much and full frame DSLRs will have a limited market.
What I originally meant with my thread was in half decent lighting condition, iPhone 6 took a better picture than my Nikon 1 J3, which is a mirrorless camera. Of course, there are other mirrorless cameras with better IQ, but the fact that iPhone images even comparable to ANY mirrorless camera is pretty impressive to me considering all the physical limitations.
I think what myself and other are saying is the Nikon 1 isn't the best representation of what a mirrorless camera can do. It has a relatively small sensor compared to the other options.
When you're talking low light, sensor size along with size your aperture on your lens, and whether your camera or lens have image stabilization are the primary factors in determining how great your image is going to come out.
I don't think I've used my flash on my NEX-5T yet because I have a 35mm 1.8 aperture lens. It has a largish APS-C sensor so it is pretty decent in low light. (and again for what it is the iPhone 6 does very well here as well, but my sony is in a different league). Using this camera in low light isn't making up for mistakes or technical flaws, it's allowing me to get better shots in conditions where it wouldn't otherwise be possible. Using a flash is always my last resort.
Whether something is a mirrorless camera or a DSLR is of no consequence in this area. If you have a Fuji or Sony mirrorless you have the same size sensor as what's in a DSLR (Fuji is strictly APS-C and Sony makes both APS-C and Full frame sensors). I haven't used one myself but apparently the Sony A7S can practically shoot in the dark, because its a full frame sensor and the fact that they've done some amazing work to optimize it for low light (it's a lower megapixel sensor with larger sensing areas).
So it's great you're happy with your iPhone, but you may want to look to a different mirrorless camera if you want to step your pictures up. My point is just don't feel like you need to go to a DSLR to do so. There are very few advantages left with DSLRs (verlon mentioned a few of them)- if those don't apply don't worry about it, get the newer technology.
The one thing that hasn't been mentioned in any of this is having a live view of what the sensor is actually seeing after the camera has done it's processing should actually be the primary advantage given for mirrorless cameras. When I had my canon, I'd frequently be disappointed with how pictures came out later because it looked great in the viewfinder when I took it, but it's not how the sensor saw it. Now with my Sony I have a pretty darn good idea of what the end result will be.
