Airbii have wingtip fences, well I think BA might have some of the old 320-100s that don't but let's leave that aside

Now, when you see the wingtip fences (small winglets) and know it's an Airbus, the 319 has one overwing exit, 320, 2 overwing exits, and 321 no overwing exits, just 4 doors each side.

737s have no wingtip fences (as far as I know BA has not outfit any with the aftermarket winglets either). Engine intakes are oblong at the bottom as well, vs. airbus.