Do you qualify with points and do you need the 1.5 EQP for qualification? If so, that can be a good reason to choose WT+.

If not, I agree with Microwave that JFK-LHR is a short flight and I wouldn't pay the extra $500 for WT+. I've flown WT+ a few times on the kangaroo route and it's not a great product IMO. I might pay $500 extra when flying the kangaroo route, but not for the hardly long-haul JFK-LHR.

For comparison, Qantas on the other hand has an outstanding PE product and I regularly pay up to around $600-$800 premium r/t for TPAC in PE. But EQP requalification plays a big role in that decision for me (especially considering Qantas' abysmal economy AA miles & points earnings).