W2K is very different. PnP, ACL inheritance with NTFS5, Active Directory… Active Directory alone is huge.
As far as certification goes, MS knew that NT4 MSCE was becoming a joke and they changed the test for W2K so that you actually had to know what you’re doing to pass. But I still think that the attitude hasn’t completely shifted on this. MCSE may get you more interviews, but you had better be able to back it up during the interview.