My main device for serious digital photography is my Fuji T2 and my 100-400 with the crop factor converts to a 150-600mm which is perfect for the wildlife photography I do.
I have also been using my iPhone the past couple of years for my technical documentation work and been pleasantly surprised on the quality of the images.
In the end, it’s about what works best for your needs. I have seen some amazing photos being generated from the newer iPhones and it only going to get better.