I don't have especially high hopes for Cloud 9 given that Fnatic already proved themselves to be a better team and have measurably improved since their last meeting, whereas Cloud 9 have been relatively static. That said, it's possible the drumming they got on the world stage knocked them off - well, you know - and got them back in the lab working on stepping up their game.
There's also the open question of who the current patch changes better benefits. They were both teams that were very comfortable and happy playing on Season 3 (and demonstrably less so on Season 2), but for very different reasons. I definitely feel that the current mid meta is to xPeke's clear advantage and it seems likely sOAZ will adapt better to the toplane meta shift than Balls, but aside from that it's a bit of a toss-up; last time I saw Rekkles playing he had adapted very poorly to the meta shift, but I don't expect Fnatic's bottom lane has actually gleaned much from it, either. The jungle changes feel slightly more in Meteos's favor, though, given that he's always been farm-heavy and fancied himself a carry compared to others.
I'd still give it to Fnatic overall, but it should at least be worth watching, unlike the two NA/EU sets we've had so far. Those were practically just showmatches to let the big dogs roll out their flashy new rosters against total jobbers. (Big ups to Dig, though, when it comes to taking the fall so other teams can get over, they're top notch.)