Cao Cao will win—though it's something Xun Yu doesn't want to say outright. The biggest difference between him and Chen Xi in changing celestial phenomena is that he does so actively, while Chen Xi does it passively. The most terrifying aspect of the Northern Desert is its storms and blizzards, but Xun Yu's ability is sufficient to alter even the celestial phenomena of the Northern Desert!
Although he can only change the distant celestial phenomena for a short time, it's enough for maneuvers around the Northern Desert. Five hours of respite in such harsh conditions is sufficient.
Ma Chao originally intended to lead his troops through the Northern Desert. To understand this, one must realize that during a time when the roads are blocked by snow, it's entirely different from when Huo Qubing traversed the Northern Desert in autumn years ago. At that time, if survival was one chance in ten, now it's practically none, at least for those soldiers of the past.
