i've heard great reports from people flown bizelite to TLV that it was a great flight. these are on DL's B777's which are pretty new & decked out. unlike CO's B767 Biz which many prefer over DL's 767, the biz on DL's 777 is compareable to better than CO's.
from your post it seems DL's pro's are:
200$ cheaper, better connection.
VS.
25% more extra miles, preference to CO's domestic F.
consider that
ATL-TLV is +/- 12 hrs (return +/- 15)
EWR-TLV is +/- 10 hrs. (return +/- 12)
choosing DL would also give you a longer leb of the biz portion of your ticket.