I think that Alonso will win because he’s much more adaptable than Kimi. Kimi has a small operation window where he is very fast, but he tends to struggle a lot when the car doesn’t suit him. Kimi has struggled many times in the past with steering issues and suspension geometry. Kimi’s lack of adaptability was most obvious in 2008 and some races of 2012, where he was out-paced thoroughly by his teammate.
Alonso on the other hand, well, he can pretty much handle anything. Twitchy steering, bad brakes, jammed clutch, broken gearbox, cold tires, you came it. You can throw anything at Fernando, but it wont stop him from reaching the podium.
A characteristic about Ferrari’s past few cars is that they have been far from perfect. Under these conditions, Alonso excels while Raikkonen struggles.