Hamilton is the faster driver, but Button has been able to make more of his situation.
In Australia, HAM was better, and in Bahrain, quite a lot better. But in the other races, slight edge for Button, mostly because of his race sundays.
In my database, their average is the same (7.6), HAM has a slight advantage in consistency, but I feel BUT did better in Malaysia and China than HAM in any race of the season.
Rosberg is hurting in the ranking because of the tough day he had in China, for which I gave him a 5. He showed a learning curve in the last race, compared to Bahrain. Sutil has had real bad luck and possibly would have finished in front of Di Resta in some of the last races. He has had no bad weekend yet (a 6.5 in China was the lowest in my database), contrary to Rosberg.
In general driving ability, this would not be my ranking at all. ALO would lead VET, but his unfortunate weekend in Malaysia is still hunting him.