I also prefer West Coast Nikon. When I'm home in LA I just walk into their new location on Apollo and they take very good care of you. I live in MI most of the year and still send my gear to West Coast Nikon because I have always had a great experience there.
I did not know if one service center was better than the other. I know with Watches (Omega, Rolex) it can make a big difference on which service center you use.
Looks like I will be using the EL Segundo service center.