1. Delta.
http://www.elal.co.il/default.asp?V_DOC_ID=1385
*member of El Al clubs will not be able to earn points on DL marked flights en route Tel Aviv - NYC - Tel Aviv.
2. That is the question for every codeshare flight. DL might offer better prices, or one-ticket connections that ElAl does not offer.
You will probably not get the perks of a Delta Elite (if you are an Elite) as it is another carrier. Not sure about ElAl perks if you are gold or Platinum.
[This message has been edited by apirchik (edited Nov 18, 2003).]