When it comes to astrophotography, assuming that is your primary focus, you really have two options: A full-frame DSLR, or a dedicated monochrome CCD camera. A dedicated CCD camera will generally take much better photos, and give you far more control, for astrophotography alone (particularly deep sky, but with focal reducers a short focal length telescope can become a pretty nice wide field lens.)
If you also want to take regular photos, and still want the best camera you can get for astrophotography, then you should look at a full frame DSLR. In particular, the Canon EOS 6D. The 6D is a very reasonably priced full frame camera (in the US, it currently sells for around $1400), but it also has some of the cleanest high ISO noise to be found outside of the Canon EOS 1D X (which sells for almost $7000!)
The very, very clean, low level of high ISO noise on the 6D, combined with its relatively large pixels, make it an ideal astrophotography camera. It costs about the same as a dedicated high quality astrophotography CDD, but is far more versatile as it is a regular old DSLR as well.
If you need a more capable camera that still offers low noise at high ISO, and you have more money to spend, the Canon EOS 5D III is probably one of the most versatile cameras on the market. Similarly, the Nikon D800E, which is priced similarly to the 5D III, offers more resolution and finer detail, which can be a boon for astrophotography. Neither the D800 nor the 5D III have quite the level of quality the 6D does when it comes to high ISO performance...the 6D is VERY usable up to ISO 3200, and still quite usable at ISO 6400 (where as by ISO 6400 the 5D III will start eating up higher magnitude stars.)
If I had to recommend the single best device for photography+astrophotography, it would be the 6D. Great price, very versatile camera, excellent IQ at high ISO...the only way to do better (at the time of this writing) is buy a dedicated telescope CCD camera.
Historically, astrophotography before the digital era could be done on a variety of film cameras. The use of a medium format film camera was not a necessity, although you certainly had a larger frame which could be useful. Doing astrophotography with film these days is probably more difficult than with digital, and certainly more costly. You have to deal with reciprocity failure, so calculating how long you need to expose to get the exposure you want can become a little difficult for longer exposures (i.e. exposures on a tracking mount.) You also incur the cost of buying the film and having it developed, where as with digital you can do it all yourself with your own personal computer and some tools like Adobe Lightroom, Adobe Photoshop, Deep Sky Stacker, Registax, etc.