Id do BA J over LH J!

Only if there was some sort of sale on would I take LH J - or I could avoid a change.

Its a very odd question as it implies all things are equal. Given your routing - what is the price difference?

If its the same price , why wouldn't you take an F cabin unless you need the Miles and More points? Id probably pay up to £1000 more for BA F (£500 each way).