This article does a good job of explaining how Ferrari's PU advantage is worth about 2 tenths of a second in qualifying.
In race trim, it seems Merc and Ferrari are pretty even on power with Mercedes holding an advantage with respect to fuel efficiency (which supports the claims indicating that Merc's ICE is slightly superior).
"In qualifying, the Ferrari was gaining 0.6s on Mercedes down the straights and the Merc was clawing only 0.4s of that back through the corners, a very different trade-off to that seen at more conventional circuits. With both engines in race modes, around 0.2s of Ferrari’s qualifying straight-line advantage disappeared – giving them near-equal lap time capability on race day, but delivered in different ways."
https://www.formula1.com/en/latest/arti ... qbg1o.html
W10 rear suspension:
Compared to W09 rear suspension: