For Kobe's part on defense, there are numerous examples of where his defense directly influenced a series (positively

). Off the top of my head we have the battles with the Thunder where Bryant being placed onto Westbrook instead of Fisher (or Sessions) completely changed the tone of those series. In each series against the Celtics, the Lakers noticeably performed better when Kobe was on Rondo. Additionally, he also at various times (more especially in the '08 series) had to guard Allen and Pierce as well at various times and did a more than solid job.
In 2011, a hobbled Kobe was tasked with guarding a scorching hot Chris Paul towards the end of a surprisingly difficult series against the Hornets. He didn't shut him down, but his absence level of play in the prior games was not seen again if memory serves right. And I remember his team defense being terrific in the '09 Finals against the Magic.
I think with all the criticism Kobe gets on the defensive end, we forget how surprisingly versatile he is. I say versatile because he seems to be able to guard smaller guards with more often than not a good amount of success. He's had to guard Rondo, Westbrook, Lawson (forgot to mention him) and Paul among other players and that's just from the more recent years in the Playoffs, ignoring his defensive peak in the early 2000s (mostly because I don't remember as well as I do the recent years).
Not to be forgotten is the Lakers team defense, which was very good to excellent at times, but I think that's a trump guard people play to often to downplay Bryant's ability on the defensive end. There's reason why Bryant was placed onto these elite players and the Lakers afterwards had success after the switch.
I'm saying this because I'm a bit shocked that people are kinda suggesting that the defense between Kobe and Dirk is a toss up. And I like Dirk defensively, despite having a so-so reputation on the defensive end. But I don't believe Dirk has ever changed the course of a series with his defensive placement in a given series as often as Bryant has.