Maybe Gibbs is a better shot since he has all those years of experience.To me that isn't true NCIS Los Angeles has way too much gunfire and explosions. Where 1 aimed shot should do the job they empty a clip. Gibbs places one shot and except for bullet proof vests enemy is down.
I also think that NICS is geared to a more older crowd and NCIS L.A. is geared to the more younger viewers ,who like all the flash and booms that an action movie has.