So Hans, "Todd" is your screen name on that other Board?
Wish I had the resources to purchase and the time to listen to so many sets...
Really! I wonder if "Todd" ever listens to anything else?
As I know nothing about the Yves Nat set, I (quickly) read Todd's review and it's rather mixed. His review of the Stephen (Bishop) Kovacevich set, which I've never heard either, is mainly negative, especially regarding the later recordings in the set - and so is the review of Jan de Kruijff, one of the foremost Dutch classical music journalists. The earliest (i.e. early 1990s) recordings in Kovacevich's set seem to be the best by far.
On the other hand, the latest Penguin Guide gives the complete Kovacevich set a rosette and says it's one of the best available, and an earlier edition gave his individual disc of 26 and 29 both a "key" AND a rosette and specifically said his Hammerklavier is one of the best ever recorded. So I guess it's just a matter of taste--or pride in a pianist now living in the UK.