Button:
R1| Qualified 8th, Finished 7th, overtook nobody when he needed to
R2| Qualified 4th, Finished 1st, fortunate enough not to need to pass anyone
R3| Qualified 17th, Finished 8th, overtook Alonsos struggling Ferrari and the rest in pits or mech failures
R4| Qualified 5th, Finished 1st, fortunate enough not to need to pass anyone but Rosberg
Hamilton:
R1| Qualified 4th, Finished 3rd, passed Vettels struggling Red Bull
R2| Qualified 11th, Finished 6th, passed Button, Webber, Massa before being wrecked by Webber when in 5th.
R3| Qualified 20th, Finished 6th, passed 5 people on track, plus 7 on grid straight incl Button & Alonso
R4| Qualified 6th, Finished 2nd, passed approx 10+ people (midpack folks)
This isnt intended as a Hamilton is better than Button and heres the proof (though FTR IMO anyone who doesnt recognise that as being true anyway is blind) but just a bizarre observation from the first 4 races of the season. Its quite easy to say bloody hell Jensons doing well at the moment, 2 race wins, tops the driver standings etc. But when you analyse what he's done what he's actually done is actually just make 2 very good decisions which have won him races, and the other 2 races he's spent his time following others unable to pass them. The 2 races he'd won, its hard to judge as he found himself in the that position in the first few laps so didnt have the chance to prove he COULD have passed people, but in the other races he proved he COULDNT pass people.
Im sure the fact that they're having to compromise on the setup to give it better balancing and this isnt making them as fast as they could be is a factor which could soon be solved in Barcelona, they could both be overtaking with relative ease if DF is equal to the rest of the grid and the F-Duct gives them a straight line speed advantage as you'd expect (currently they're adding extra DF, which the F-Duct neutralises down the straight, meaning no speed advantage but hi-DF with no speed loss like all other cars would experience).
As for the 'yeah, well he did it last year'.... its quite easy to overtake people when you have one of the fastest cars on the grid, and thats my point. He's having to fight for passes, and he's struggling. Hamilton is too, but the difference is he has made a dozen, including Button, Massa, Alonso & Webber (+ Vettel, but in a struggling state) and thats what you expect from world champions. The likes of Senna, Prost, Schumi, Alonso... they can hussle a pass with witt & cunning maneuvers. Button showed last year he could win from the front in a dominant car, and win when a faster car (RBR) appeared and had a dozen mechanical issues... he rarely took a race by the scruff of the neck and faught for it (Brazil is the only occasion which springs to mind). Maybe thats not his fault, but it doesnt disprove my point either.
Also regarding someones 'one of a few to pass a KERS car' pull the other one, half the grid passed a KERS car at some stage. Their extra weight compromised them around 80% of the lap, so made them vulnerable where most equal cars wouldnt be, and while they're hard to defend against, it wasnt as hard to pass one because there was more opportunities (due to more defensive lines being used around the track) and being slower on the corner exit if you were still close when the KERS was deployed you'd probably be able to stick with them in the slipstream. It certainly wouldnt be like comparing single & double deck defusers, KERS was removed from many cars frequently, only McLaren ran them regularly and still removed it for a couple of rounds (Silverstone i recall, due to not enough brake points to recover energy) so many teams removing it showed it wasnt all that.
Jenson is a very good driver, many will say he's one of the best in F1, but IMO his racing ability isnt of the standard you'd expect from a WDC and he's done little to prove that. Many people were saying this at the latter stages of last season, Brazil surprised many people, but its the exception and not the norm. Vettel was a far better racer, but had mechincal issues. Jenson got the WDC exactly how you're meant to, winning races and picking up pts... you cant knock that, but IMO its the weakest WDC winner i can recall for a long time (i've watched since late 80's) but again... not his fault, he raced, won, and did so without controversy.