LeBron gets to the rim and draws fouls, which Kobe does not do enough.
Kobe is a better shooter and arguably a more complete scorer, but talent alone does not anoint one player over another in this league.
It bugs the hell out of me to see LeBron draw phantom fouls everytime he commits to the rim and throws his hands up like he's been raped. But he's still the best penetrator in the league in my opinion, because his combination of speed, strength, athleticism, and explosiveness make for a matchup nightmare. And he can still shoot - albeit, inconsistently - but when his shot is going in from outside, he's as dangerous as anyone.
Kobe will either help you win or take your team out of games with his shot. Someone like Pierce doesn't need to shoot the ball particularly well if he's passing and rebounding efficiently, as well as playing good defense. This entire season is evidence of that. Kobe, on the other hand, seems to directly affect his team's success, and in these Finals games that was seemingly the case. More talented player one could argue, but he just doesn't have that "it" factor to propel him above the likes of LeBron. But one must be careful not to rely just on stats because there is more to stats than at face value.