It depends. For NYC big law, the gap between H and CLS/NYU is probably not huge, although the rarity of YLS and SLS grads still insulates the bottom of their class, relative to CLS/NYU where a significant number of people get a big firm job.
For some "snobby" jobs, however, there is a real gap between HYS and CCN. Williams and Connolly has 48 attorneys from HLS, and 9 from Columbia. At Covington DC, it's almost 100 attorneys from HLS and 19 from Columbia. I did OCI in DC, and it was quite clear that T14 was the minimum requirement to play the game, CCN, except maybe Chicago, wasn't considered in a different league, but HYS were considered legitimately prestigious.
LawClerkAddict used to track some good data:
http://lawclerkaddict2009.blogspot.com/
For 2008, the top appellate judges hired:
"The Dozen Most Prestigious Federal Appellate Judges:
Boudin: Harvard, Harvard, Harvard, Yale
Calabresi: Cornell, Harvard, NYU, Yale
Easterbrook: Chicago, Harvard
Garland: Harvard, Harvard, Michigan, Yale
Kozinski: Chicago, Harvard, Northwestern, Tulane
O'Scannlain: Cornell, Virginia, Yale, Yale
Posner: Chicago, Harvard, NYU
Reinhardt: Columbia, Harvard, UCLA, Yale
Sentelle: Duke, Harvard, Harvard
Tatel: Duke, Georgetown, Stanford
Wilkinson: Northwestern, Stanford, Virginia, Virginia
S. Williams (Sr.): Berkeley, Chicago, Yale"
That's 12 Harvard, 7 Yale, 1 Columbia.