If you are confronted with a Prädikat Riesling from Germany, you may be asked to identify where it comes from specifically. Here’s a way to approach the process of narrowing down your options.
While Rheinhessen does produce plenty of off dry/medium sweet wines, they are less regularly seen than those from other regions. In general terms, Rheinhessen is warmer than Rheingau, Nahe or Mosel so more Trocken is produced here. As such, I would probably discount Rheinhessen from the conversation if you have a Prädikat wine.
That leaves the big three: Mosel (including the subregions of Saar and Ruwer), Nahe and Rheingau. Let’s look at the identifiers for each when it comes to Kabinett, Spätlese and Auslese.
Mosel: featherweight wines which walk the tightrope balancing sweetness and acidity. Delicate and even ethereal at times, particularly from the cooler Ruwer and Saar tributaries.
Nahe: everyone forgets about Nahe, but there are some exceptional Prädikat wines from here (Dönnhoff, Diel etc). It’s a slightly more powerful style than Mosel, and while it does enjoy plenty of tension and slatey minerality, it’s not quite as poised or nervy as Mosel - it’s just a touch riper and rounder.
Rheingau: more powerful than either Mosel or Nahe. The wines are broad shouldered, full of fruit and richness and may be a degree or two higher in alcohol. These are not wines of tension but instead of breadth and concentration.