Both are alltime greats and the media will put Kobe higher but the fact is Duncan's career is as good if not better.
PER is used by many to try to weigh the value of a player statistically, besides more MVPs and finals MVPs= Duncan of course top ten all time in PER while a plausibly overrated SG named Kobe is 17th.
http://www.basketball-reference.com/...er_career.html
Duncan 4th among active while Kobe trails: LeBron, Wade, Paul, Duncan, and Dirk
1. Michael Jordan* 27.91
2. LeBron James 26.94
3. Shaquille O'Neal 26.43
4. David Robinson* 26.18
5. Wilt Chamberlain* 26.13
6. Dwyane Wade 25.65
7. Bob Pet * 25.35
8. Chris Paul 25.23
9. Tim Duncan 24.84
10. Neil Johnston* 24.63
11. Charles Barkley* 24.63
12. Kareem Abdul-Jabbar* 24.58
13. Magic Johnson* 24.11
14. Karl Malone* 23.90
15. Dirk Nowitzki 23.73
16. Hakeem Olajuwon* 23.59
17. Kobe Bryant 23.53
18. Larry Bird* 23.50
19. Kevin Garnett 23.43
As PER also shows Shaq not Kobe was the prime reason for LALs three les in a row and even with Gasol (28th all time) aside him Kobe could not deliver without Shaq to a similar extent. Kobe has also lost finals - Duncan has never lost a finals.