Personally Id choose the A340 from a rarity point of view,and also the 2-4-2 config,the 747 wins for speed,i gather on a typcial HKG-LHR flight its 45 mins faster than the airbus.

I flew Premium Economy on a Virgin 747-400 and it was 2-4-2 (in the small section on the main deck behind Upper Class) and 2-2 on the upper deck. It’s only 3-4-3 in Economy.