I think that both Ferrari and Vettel will be in for a disappoint. The Ferrari won't be quick enough, and Vettel won't be able to extract as much performance from a mediocre car as Alonso could. I don't see this being a fruitful partnership.
I kinda see it differently. Not about the differences between Seb & Nando, which I happen to agree with, but because of these differences. Seems an odd thing to say so let me explain my theory.
Alonso manages to mask just how awful a car is and in so doing gives the designers and engineers of that car and power system some comfort that they are going in the right direction, whilst in reality the car is really a dead horse that needs to lay down.
Where as Vettel and others who appear unable to make bad cars outperform their limits quickly show up 2nd rate machinery, with low or no point scores, causing any team with a big budget to look for a more clean sheet approach for upgrades, or even a mk2, rather than the sequential steps teams like to adopt.
Just my theory, but perhaps Nando has suffered more than most because of his own higher ability in the last few years.