Do you do that route often?
I'm currently debating between VS45 (LHR-JFK) in the old A340 and VS1 (LHR-EWR) in the brand new B787-900.
They would both be in Y but the latest would mean paying an extra $40 for a taxi.
It would be my first time on the B78-9.
Is it worth it?
Just flew VS 3 &4 in Y on the A340, it's old and cramped but we had ghetto uprgades and didn;t notice too much
we also flew the b787 LON- JNB, which had more room in Y, less bathrooms and only slightly better entertainment system
for a y trip the motto is Veni Vidi Vivo (i came, i saw, i lived)
in answer to your question, if the flight is packed (it usually isn;t) it may be worth the $40, if not dont bother