i am sure someone will be able to give you a very detailed technical answer to this question...i doubt it will really tell you more then me saying: it is quite a bit better!
leaf lets you download tons of raw files, other makers are less open about their raw files...the problem is that the only way to really compare files is to shoot the same scene side by side with the cameras you want to compare...i know michael has his DVD for sale, which is great, but in my opinion tabletops don't really tell me that much about DR or shadowdetail or even color and skintone, all the things most important for me..resolution is secondary for some people (and a lot easier to capture and understand with numbers)...
anyway do yourself a favor and rent a MF back...don't worry about resolution...most backs have the same DR and color, some simply have bigger chips...if you are contemplating spending 20,000-35,000, a couple of hundred should not make a difference....call up a dealer, ask for a demo in the store, bring your DSLR, shoot the same setting, take the files home...compare...shoot the wall, shoot the sales person, shoot into a lightsource...compare...
any MF back will give you just about the same DR...the difference is very obvious...