I've got an Pentax K-r DSLR camera (tech specs here). This camera is about 9 years old. And I have the stock 18-55mm lens. I've also got an iPhone 11 Pro (tech specs here).
Both have circa 12mp sensors. Which sensor is better? And which camera would ultimately produce a better image?
I intend to use either for some interior photography, so it's a 'planned use' rather than an ad hoc requirement. If using the iPhone, I would do it using an iPhone-to-tripod adaptor.
Use both. Use whatever is fun right now.
Depending on the situation, one or the other will be better.
A DSLR tends to give results that are just the photo + very basic and deterministic postprocessing (you are free to postprocess it on a computer), while smartphones cameras try to be smart and sometimes phony with the postprocessing.
A DSLR is more weight to carry but, with practice, can be much quicker in handling, especially when you want to work in semi-automatic and manual modes.
Subjective, out of camera image quality will likely be better with the phone, at least by contemporary "beauty standards" for a photograph - however, both options will yield more than enough image quality for most users.
Theoretically, the much larger sensor will be at an advantage in image quality and lowlight capability - however, device ages will about level the playing field here.
DSLR/mirrorless photos tend to look good when viewed full size on an HD or better monitor, or printed ... smartphones tend to optimize their output towards having great impact in smaller formats (web images among others on a web page, screens of other smartphones). This becomes even more apparent when looking at enlarged portions (or cropping a part of the image out!).
What WILL make a DSLR lose out to a smartphone is a mediocre zoom lens - get something like a (used) f2.8 zoom lens and/or reasonably modern prime (vintage primes have their merit but they tend to have a strong "character" that will sometimes make, sometimes break your picture). If you have the 18-55 DA WR (just a guess with that camera...) ... not horrible, but not the best that camera can have mounted to it ;)
Usually, one weakness of smartphones is telephoto operation (less so with a multi-camera phone like you have) - however, you can fit a 400mm or 600mm lens to the Pentax, not so much the phone.
One or the other option can be better accepted to use in social situations - sometimes, the smartphone user will be more accepted, in other cases it is better to be mistaken as a serious photographer or press guy.
One disadvantage of consumer DSLRs like the K-r is that these have two precision problems, compared to mirrorless cameras and smartphones - the viewfinder frames inexactly (the specs say it is a 96% viewfinder), and there can be autofocus precision problems (mirrorless cameras and quality smartphones autofocus using the image sensor itself as a reference. DSLRs use a separate sensor for that, and these two sensors can go out of whack with respect to each other).
The Pentax has two advantages to many other (even current) DSLRs, that it has in common with smartphones: It is designed in a somewhat weatherproof way (Pentax is reputed for that, even though the K-r is not sold as a weatherproof camera), and has an image stabilizer.
In terms of image quality a larger sensor (of the same generation/technology) always wins because it gets more light (same composition/SS/Ap). It is also less demanding of lens resolution.
The I-phone has a sensor that is just over 7mm long edge, the K-r has a sensor that's just under 24mm. That's ~ 9x the size in area, and ~ 9x the amount of light/information. It also means a detail can be recorded 9x as large (area) and still be just as sharp. Granted, the generations/technologies are a bit different; but I highly doubt any phone sized sensor can overcome such a handicap.
The sad truth, for those of us who have invested in 'quality' photo equipment, is that if the phone has the necessary field of view and you don't intend to make poster-sized prints it will probably do the job just fine.
But it's easy enough to try. Take some pictures today. Your house is a good enough subject! Let us know which did the better job for you. If there's no practical difference, go with the more portable option I suppose.
