There are a lot of factors that go into a winning season.... division, park, talent, all of that. The A's have all the advantage in the world over the Giants simply because of who they play in their division. The A's are doing good, dont get me wrong, but if the Giants were in the AL West, and playing the Mariners and Rangers a billion times a year, they would be dominating, too. Also, you are in second place in, probably, the worst division in the league. The Mariners and Rangers are two bottom-dwellers... possibly in the worst five teams in the league. Just keep in mind that the Giants are playing the Rockies and D-Backs over and over again, in addition to the Dodgers, who have talent, but just havnt put it together yet.
So, yeah, keep in mind the fact that, no matter what, you cant tell the better team by the record. Obviously, though, the A's have been playing well so far, and they are probably more talented, not to mention younger.