Many Asian airport gates are setup with two boarding doors, one for FC/BC and one for coach. With dual aisles a 744 boards pretty quick. I would say quicker than a 753.

The A380 will have two floors, two aisles each, thus a total of four aisles. With two entrance doors - I think the boarding will be quicker than many large jets today. The hang up in the boarding process tends to be blocked aisles. Four aisles is going to help.