Hi everybody,
sorry I couldn't log in earlier to respond.
First of all I would like to thank you for your advices & responses.

I forgot to mention that 50% of my flights are TLV-LHR, and 50% TLV-US (excluding family trips and maybe 1 flight to somewhere else in europe a year). All of these flights are in business class (or CW, if flying BA).
Therefore, as for the soft benefit of priority in op-ups, I'll only get it in about 25% of my flights (LHR-US).

I have experienced myself great service by BA's office in TLV. For example, there was a time they had a system glitch and didn't give me a credit for a flight which I upgraded with miles, so the supervisor at BA call center in TLV also gave me 25000 avios (than miles) as a compensation.
However, I've also experience good (but not great) service with LY. They usually open up award seats if needed (without charging double miles, but that's after a very long wait-listing) and in my previous membership year they renewed gold for me thought if I had 1600 points (out of required 1800). However, in my current LY membership year I will earn no more than 1300 points (due to personal reasons that caused me to cancel a 700 points trip).

I also need to consider the fact that in 2014 I'll have to travel twice to HKG (leading me to only travel once to the US instead of the usual 3 times a year). For the TLV-HKG route, LY is better than BA, mostly because of the fact that the flight is direct and is guaranteed not to fly over arab countries.
Maybe this should be part of what I need to consider?

I think that when BA will change their terminal in LHR again (probably in 2014), I may give this thing a second thought.

BTW, I heard that BA has a new lounge in TLV? Has anyone been to it, and can give me derails?
Thanks.