You could look at it this way - the best sample size we actually have access to isn't 4 out of 7 games, it's the balance of the series. Over the course of 7 games the Spurs scored a few more points than the Heat. Thus, the Spurs were the better team. In general in sports we tend to value scoring margin over small discrepancies in record. This is why everyone thought the Orioles were overachieving last year - their scoring margin didn't bear out their winning record. Not like I'm making this up on the fly, sportscasters and stat guys have been saying it for years.