It's funny how I heard completely opposite about Williams testing; from what I've heard, apparently Sirotkin had better single lap times while Kubica was stronger on long runs I actually believe that both performed at a very similar level, so in the end, Williams chose the one with more sponsorship money - once again, definitely a speculation since we're in no position to know any of the actual details, but most of the sources I read have mentioned 8-12 million Euro as Kubica's sponsorship budget, while Sirotkin's team offered almost twice as much. Whether it's true or not, the team was always going to waffle about choosing the best driver based on ability and what not either way, so I guess we'll only see how he does when the time comes.