I like all the surfaces, each requires adjustments in the player's game in order to succeed.
Clay is my favorite when played with proper craft. Slow HC is the one I dislike a bit, but I can still enjoy it.
Even going back four years or so it was only Monfils sliding on hard courts. Now almost everyone is doing it. No wonder players get knee injuries.
It's a blessing Nole hasn't developed knee or ankle injuries yet. The guy really makes me cringe at times. The way Nadal slides seems safer to me but he does have the injuries.