I agree with both of those last two statements.
I think the big thing with KG is he is such a good all round player...there really is no hole in his game.
He doesn't only defend at an elite level, he does just about everything at an elite level.
Among all NBA Centers last season (per 48 minutes) KG ranked:
* 1st in assists (4.5 AP48)
* 4th in scoring (24.4 PP48)
* 9th in steals (1.44 SP48)
* 19th in rebounds (12.7 RP48)
* 25th in blocks (1.57 BP48)
Among all centers he also ranked:
* 1st in FT% (85.7%)
* 2nd in Assist/TO (1.64)
* 7th in 3PM (3)
* 9th in FG% (50.3%)
* 9th in double doubles (21)
That there gives him:
* 4 stat categories where he ranked top 5 at his pos
* 4 stat categories where he ranked top 10 at his pos
* 2 stat categories where he wanted top 25 at his pos
Basically you're looking at a guy who ranks top 10 among centers in all but 2 statistical categories (and top 25 in those) and that's just looking at simple stats.
KG is an absolute beast, but you don't realise just how good because you don't realise how much of everythign he does - and that's BEFORE you consider the intangiables (energy, communication, leadership, durability, good hands, hustle, effort level, etc).
Most importantly is that great as he is, Rondo still has flaws. He's a poor free throw shooter, his jumpshot still isn't consistent enough and he does have a tendancy to gamble on defense. These are all parts of his game that opposing players have a chance to exploit. Perfect example is when other teams double team off Rondo and dare him to shoot - while his jump shot has improved markedly, he's still yet to prove he can hit that shot consistently every night. Likewise the Hack-a-rondo concept...he hasn't shown he can knock down free throws.
Garnett really has no flaw in his game that opposing players an exploit. He has the ability to score efficiently inside and out, he's an exceptional free throw shooter, he's not foul prone, he's got good hands, he makes good decisions, he plays on both ends of the floor and he's a excellent passer out of double teams.
It's that all-round excellence that allows KG to have such a huge impact on every game. Sure, if he sits down you can replace him with a rebounder (like Sullinger) but then you lose the defense. You can replace him with a defender (like Collins) but then you are at a liability on offense. You can replace him with Bass (who is a solid offensive player and decent defender) but then you lose out on the boards. There is no one player on the Boston roster who can replace everything KG does on the floor...not even close.
With Rondo on the other hand...Terry, Pierce and KG are all solid passers, so while we DO lose out when Rondo leaves, we don't miss as as we do when KG comes back.