My money is on RBR. They had it right many times even with a bad engine. Now that the engines are quite similar and the aero and chassis building are new, I reckon RBR to have got it right.
Based on this, my heart would love to see either Dan or Max winning it. My gut tells me Dan will pull it out in the long term as he has shown many times he is a consistent driver. Whereas Max is prone to being over enthusiastic sometimes.
Alonso is there because he's Alonso. Period.