It takes the same time to verify a wrong password and a correct one. But, when the password is wrong, the operating system makes you wait a bit. This is a security feature, to discourage people who try "potential passwords" (in particular people with some electronic skills, plugging in some circuitry which the computer will consider to be a keyboard, but which in reality tries a lot of passwords real fast).
Such things don't work as well in a network context (if the attacker wants to try 100 passwords quickly, he can open 100 connections in parallel) but the password verification code is often shared between network and local logon.