I think people are mainly saying that if ANYONE can beat Sasha, it‘s Anna but at this point they just don‘t expect Sasha to be beaten. Or that‘s what I think at least. Both have made mistakes this season already, with quads you never know. In the end it will depend on who is the cleanest that day. It could be Sasha but it could very well be Anna, too. I think in general it‘s understandable that people would give the edge to Sasha, though (I would, too, even though I prefer Anna by far) since she has
1) more experience - Anna missed last season (not her fault obviously)
2) Anna made some mistakes in SP a few times already (only time Sasha messed up the 3-3 was at the Khrustalnyi exhibition and that wasn‘t even a competition so shouldn‘t really count)
That being said, I wish Anna lots of luck of course and I‘d actually prefer it if she won. Sasha is a lovely girl but her skating isn‘t really my cup of tea whereas Anna‘s definitely is. But overall, we never know. Quads are risky and can‘t really be predicted. Everything could happen, truly, but I‘m at least 99.9% sure that it will be either Sasha or Anna who‘ll be on the top of the podium with the other one in close second.