Will a digital back provide a better Raw file? Without question
Will a digital back make anyone a better photographer? Not a chance.
I started to write a detail response but the quote above sums it up.
Personally I think beauty is in the eye of the beholder. Some people love the look of a non aa filtered ccd camera, some don't , though most professional photographers select a camera weighted toward the scene, subject and project.
In the film days you selected the camera/lenses first, because any film would go into any camera and workflows were virtually equal between a Hasselblad, an RZ or a Nikon. One might shoot faster than the other, or focus easier, but they all used the same film, "sensor". Size may have a resolution difference but looks were comparable.
Today, regardless of camera the film (digital) portion of the process is equal or takes precident, more so with 645 cameras than 35mm, because most medium format cameras are shot tethered and are very software, computer dependent.
Even to get to the detailed preview, software is 1/2 of the process and will have as much to do with the look as any back, or lens.
Personally, I select a camera first, because that' the first point of contact between you and the subject. If your not happy with the camera and lens, you'll probably never be happy with the result, even if the results are acceptable.
Just FYI, the standard for all medium format cameras (not always backs) is the H series blads, at least in the digital world. Probably more backs are mounted onto these bodies than any camera twice over, so that means specialty lenses you might want to rent, or backups/repairs are fairly easy to source.
Then if I found the camera I loved, I'd start exploring the backs and their related software.
Since your in Madrid, I am sure it will be easy to do a test between a lot of systems.
This you probably know and is not really worth mentioning, but beautiful images, hundreds of thousands of beautiful images are shot with virtually every brand, every format daily so the camera is probably not as important a factor as lights, subject and talent. BTW: talent covers a lot of territory, from pre production, on set all the way through post.
Also keep in mind that web conversation is a democracy where every voice carries the same weight. This forum is no exception and you'll notice in the answers some people are more prone to loving cameras that what they actually produce, others see the camera as but a small (but vital) part of the process.
Test it yourself and do what makes you happy, because attitude goes a long way into producing an image.