Personally, I would stick with Delta.

1. Like everyone else who has posted here, I think that LY is a no-go -- its reward tickets are more expensive (in terms of flights needed to earn them) and the points you earn on any particular flight expire after three years.

2. If you are flying TLV-USA twice a month, the miles you would earn on TLV-London flights once a month will be pretty meaningless to you. Of course, if you want to earn them you can by flying AF, AZ, or KLM and connecting.

3. During the peak seasons, DL through ATL is often fully booked in Y, meaning that as a PM you have an excellent shot at an op-up. Once you land in the States, your status means you will most likely be upgraded when flying on to SFO.