The math here makes my head hurt a little (even though it's simple, really -- I'm just that dumb) but basically an analysis of a half-century's worth of title-winners shows that being a little better on defense increases your chance of winning rings more than a similar improvement on offense.
That make sense?
The implication is that when it comes to winning titles, defense may in fact be a little more helpful than offense.
On the one hand, this amazes me. How could the stats care whether I stop you getting an extra bucket, or score an extra one myself? Isn't a two-point lead a two-point lead no matter how we got there?
On the other hand ... there are trends in how things happen, and they're worth knowing about. And Neil Paine's research linked above shows that the trend is that teams that are better on defense win titles more often.
My first guess as to why would be that offense is more volatile than defense, because it's based on shooting, which is an iffy proposition for even the best shooters in the world. What that means to me is that if your team's main thing is being able to score like crazy, and that's how you intend to win, you will still have games -- every team does -- where the ball does not go in the hoop as much as normal. Those games will be losses for you against good opponents. And no doubt they sometimes occur in the playoffs, when every game counts so much. Normal variations in shooting could doom your title chances once in a while.
On the other hand, if your team plays great defense (something based more on effort and less on luck, in my theory) then perhaps you can do what you're best at just about every game, which means you ought to have a chance to win even on those inevitable nights when you can't hit a shot.
I wonder if the evidence supports the notion that elite teams have more volatile results on offense than on defense.
In any case, what I also have seen evidence of before is that to win a title, you have to be among the very best on offense or defense, and at least above average at the other. It's rough-to-impossible to be average at either end of the floor and still win a title. So while defense may be a particular advantage to teams with title ambitions, it sure doesn't get the job done all by itself, despite the title of this post.