constructors is normally a strong indicator but isn't conclusive. You could argue that Vettel really should have won last year but lost his head and the technical issues then flared up, but the Ferrari was more consistently quick across tracks. Plus Kimi is absolutely useless so doesn't really help in a constructors fight. In 2009 Brawn had a much faster car in the first half of the season and Button won 6 of the first 7 races, but then Red Bull caught up and overtook them and Button hung on to win the title despite 0 wins and only 2 podiums in the last 10 races. I think you could also argue whether Vettel had the fastest car in a couple of his title wins.