I don’t have as much experience with Keller as some of the other board members, but having tasted the 20 and 21 VdF side by side multiple times, I found myself preferring the 20 VdF to the 21 VdF in most tastings. As to how they’ll perform once aged, I’ll have to wait and see.
I think most winemakers tend to improve their winemaking year over year so one would hope that comes through in the wines