I always enter at A, despite there being no dedicated pre-check. There's almost never a line, period. And since they still acknowledge your pre-check status with a card so you don't have to take off shoes and jackets and go through a normal detector, security is a breeze also. I might be biased because I usually head to the Centurion Lounge first and often fly in/out of B or A since they are the American-dominated terminals, but there is almost never a reason for me to go to the dedicated pre-check entries at C or D/E.