Interesting comparison. If one stops it at various points, particularly apices, one finds that it is quite close with one driver being quicker somewhere and then slower somewhere else. My guess is that the better power allows the 2015 car to be quicker over the lap - certainly the straight line speed is better at the end of the straights. Acceleration out of corners will probably benefit slightly too once they're not traction limited; interestingly Hamilton is quicker at the first apex but slower at the next one suggesting that perhaps Rosberg was able to get on the power a touch earlier. Hamilton is faster by mid way along the next straight. Fascinating comparison and shows that a few tenths really is very little in the grand scheme of things unless you're a racing driver!
