We don`t know all the variables involved but I did a brief sector times analysis between Ferrari and Merc after qualy sim laps in FP2 ...
(Remember that Vettel set his fastest time in his 2th lap and Lewis did his fastest time on the 6nd lap, some 12 min. after Vettel!)
In sector 1 it`s even-steven between them.
In sector 2 Vettel gained 61 hundredths and this sector has 2 slow to medium corners (6 and 7) and 4 high-speed turns (8,9,10 and 11)
In the last sector - 3 - Vettel gained 117 hundredths and we have 2 slow corners (16 and 17) and 5 high-speed ones (12,13,14,15 and 18)
So, in conclusion, we could assume that Ferrari`s upgrades give them the upper hand regarding high-speed stuff, right?