I think there was a similar discussion when Tyros 5 came out and some said Tyros 4 had the better sounds (to which I wouldn't agree as far as I heard comparisons).
The older samples sometimes sound more direct, newer ones sometimes have more off-mic ambiance, pp and p velocity layers and things like that, which can make them sound more indirect.
I remember when I got the Roland Juno Stage in exchange for my old XP 80, I had some problems getting the Juno Stage pianos sound direct enough compared to the old XP 80 "piano", which consisted of a very short, looped fortissimo piano sample, but sounded very direct via speakers (however in no way realistic).