TBY
I find your downplaying the similarity between JV and LH interesting but somewhat at odds with what seem to me are relevant facts:
1. On the rare occasions when both Button and JV managed to finish the same race, JV was the higher placed more often than not. This would seem to indicate that the points disparity between the two was determined more by which races they finished, rather than a head-to-head superiority of Button over JV.
2. Williams lost their engine supplier after JV's WDC year and the customer Renault engine, called the Mecachrome, was a brick. His performances (and lack thereof) must be viewed in light of that fact. LH has never faced such circumstances.
3. When JB joined the team, the team had just undergone a change of ownership and a huge (50 approx) purge of team members, and the new owner was publicly criticizing JV over his salary, so the team could in no way be described as being pro-JV. Hence there was absolutely no "home-field advantage" for JV that year.
While I can't say that I disagree your ultimate conclusion, that LH is the better driver, to me, the case is in no way as clear-cut as portrayed.