The major factor in favor of MF is that the sensor can collect more light (called photons). Larger sensor more photons. The incoming light has random nature so it will vary some pixels get more light and some get less light. This variation will be less significant with increasing number of photons.
Therefore, the larger sensor can give a smoother image.
DR on the other hand is per definition the number of photons a pixel can hold, typically around 60000 and the noise reading out the pixels, typically around 15-20 electrons on older MF backs. Each electron corresponds to a photon, essentially. So an older MF back will have a DR of say 60000/20 -> 3000.
3000 is 11.5 stops. DxO-Mark gives for instance 10.96 EV (per pixel) for the Mamiya ZD-back and 11.86 EV for the Phase One P40+ black.
The Canon is a bit different, it has a very good sensor but it cannot read out the photons as well as more modern designs. DxO-mark gives DR =11.86 (per pixel) for the Canon 5DII. But, Canon has a trick! If you increase ISO, the signal from sensor is amplified, so readout noise goes down because of the amplification, and that makes taht Canon cameras hold DR with increasing ISO. Nikon D800, some other Nikons and Sony cameras are a bit different. They have the signal processing pipeline on the sensor and have therefore less readout noise.
The enclosed figure shows DR for an old MFDB, and older Canon and a very up to date Sony. You can see that the Sony is best at low ISO, but Canon wins above 400 ISO. The old MFDB is on par with Canon at lowest ISO.
I also enclose a figure that takes the difference in number of pixels into account.
DR is the actual number of pixels that the system uses. So, Sony utilizes 13 bits, Mamiya and Canon 11 bits. So when MFDB vendors talk about 16 bits it is simply a marketing term, because the last 4-5 bits are just random noise.
Now, DR is a technical term. It tells about the amount of noise but not about the quality of noise. It may be that some cameras have more ugly noise than other cameras.
Here is a quite technical discussion on the issue: http://www.luminous-landscape.com/essays/dxomark_sensor_for_benchmarking_cameras.shtml
Thanks for taking the time to reply ERIK. I must say im now even more confused. So the MF will only give me better toanl transitions due to the 16bit file though Dynamic range is pretty much equaly or only slightly better then a 5dmkII?? If that is the case then why would a landscape photographer go down the MF path??