I'm often asked why I shoot so many of my photos using medium format. I mean, it's SO heavy, right?
Yes. It's pretty heavy, even compared with a Nikon D5 with a long lens attached. But I didn't get into photography for comfort. I got into photography for perfection. Now, I realize I'm extremely far off from ever having taken a "perfect" picture, but that is always the goal. Medium format makes that more possible in several ways.
Tonal range is probably the most important to me. When you shoot with medium format, the sensor is much larger than a full frame or APS-C DSLR. Even though you can buy very high resolution DSLRs, they are cramming the pixels into a much smaller space. That means the DSLR, while it may even have the same megapixels as medium format, simply can't collect as much light. Larger pixels collect more light and produce less noise. On the Hasselblad H5D-50c, the pixel size is 5.3 microns. On a comparable DSLR, that is around 4 microns. That's a huge 28% difference in final product. This equates to 14 stops of dynamic range in a 16 bit file.
Depth of field. There's a fair amount of debate about the actual physics of depth of field in medium format vs DSLR. However, the proof of medium format's dominance is evident in every photo. The fact that medium format lenses can be so large is exactly the reason. Large lenses are much simpler to design and build (although much more expensive). Cramming optics into a smaller space requires compromises that medium format just doesn't have to make.
Certainly DSLR photography has it's place. When I shoot weddings, the actual ceremony and reception are always shot with DSLR. Medium format is not remotely suited for action. However, when I do formals and bridal portraits, you can bet you'll see the Hassy in my hand.