Re: Garnett's defense vs Mchale's defense
I don't think this is a legitimate comparison. There are 3 big areas of defense: defending your individual assignment, team defense, and rebounding. Mchale was excellent at the first of those things, but he never demonstrated an elite level at either of the other two. Garnett, on the other hand, ranks out among the best in NBA history at all 3 areas. That's a huge difference.
And all 3 are very different areas of strength. Being a lock-down 1-on-1 defender is a very different skill-set from being a dominant defensive team anchor. Mchale's long arms allowed him to play a step off of the quicker players on the perimeter and still bother them, or to tangle up the bigger centers. And that's admirable. But he never demonstrated the kind of foot speed, leaping ability, and defensive leadership ability to say he could anchor a defense. And you can't just assume that he'd have been able to.
Likewise, Mchale never averaged even 10 boards per game despite playing at a much, much higher pace than Garnett who is one of the few folks to lead the league in boards 4 straight years. True, Mchale had better rebounders on his team, but it's beyond a huge leap to just assume that on a different team he would go from a pedestrian rebounder to a historic one. Again, considering Mchale was often defending perimeter players (like KG) means that he was often far from the rim, and he never had the kind of athleticism to consistently get from the top of the key to the rim in time to grab 13 or 14 boards per game. That's too big of a leap to just take on faith.
Mchale was a very good defensive player. But Garnett is very arguably the best defensive forward that ever lived. I just don't see how it is remotely reasonable to say that Mchale was anywhere near equal to Garnett on defense.