You will choose DSLRs if you want to take better photos than you are taking with your smartphone, and / or you want to do more experimentation with images using advanced camera options. Basically DSLRs have better image sensors than smartphoens and simple point-and-shoot cameras.

What's more,  quality DSLRS will even teach you how you can be a better photographer - they will guide you through their various shooting modes, using hints and guides integrated in their control menus.

The best entry-level DSLR: Nikon D3300 (best image quality, the longest battery life, easiest to use.)
The best entry-level DSLR for beginner videographers: Canon EOS Rebel T5i (touch-screen swivel LCD, silent autofocus lens, and video-friendly controls)
The best entry-level DSLR for the photo quality conscious: Pentax K-S2 (great still image quality) 

Mid-range DSLRs: They have more external controls, more granular settings, custom shooting modes, and other tools that more experienced users will appreciate. They are also larger in size.They come with a LCD info screen on the top of the grip side of the camera, so you can change settings more quickly, and they use less battery than a rear screen.

Mirrorless cameras vs DSLRs: Most mirrorless cameras are smaller but provide the same image quality as entry level DSLRs. Most good mirrorless cameras come with touchscreens, Wi-Fi integration, and focus peaking. They are also less pricey. However, mirrorless may focus less slowly than DSLRs.They being smaller, you may find holding them still for longer periods uncomfortable.

Moreover, mirrorless cameras have fewer lens options. You have to depend upon electronic viewfinders. Overall, enetry level photograohers may prefer mirrorless cameras.