Originally Posted by
ajamieson
Aircraft size doesn't matter, but rather the next destination of the aircraft which are always parked on the stand relevant to their next departure.
If you happen to find yourself on a 321 on a domestic flight into LHR, it's likely this will be a mid-haul plane on a fill-in trip, so the chances of this being put on an international gate for its next flight is greater than for a 319.