We didn't see the entire fight with Atobe and Sanada, but you can be sure he didn't use SoSA, and he probably used 2 or more of his FuuRinKaZan. Also, if you go back to the Atobe v Ryoma match, you can tell Atobe didn't even go all out against Tezuka. He wanted to break Tezuka, winning seemed to come second, which is kind of strange when it comes to Atobe. Sure Atobe had 2 new moves against Ryoma, but Ryoma pushed him to use his attack style tennis, which is better than his normal defensive style against very strong opponents. He didn't use his attack style against Tezuka, and he probably didn't use it against Sanada either. Also, Atobe used Higuma Otoshi against Ryoma's SoSA Invade like Fire. Of course he could probably only do this as Ryoma is physically weak than Sanada, but he might be able to pull it off against Sanada. I am not stating that Atobe is stronger than Sanada as a fact; just saying this is what I think.
I also think Hakugei requires a topspin. Fuji "could" do a reverse spin Tsubame Gaishi, but I think that requires an insane amount of backspin. Atobe is normally defensive and so is Fuji, but then they switch when they were in very important matches. And is Fuji has 2.0 Counters; I have a feeling he can do disappearing server 2.0 later on. Over head Disappearing server =), sounds like pwnage to me.
I just think it like it is.