nomadmax 

The larger pulleys do need more chain length for the same gearing set up as the smaller pulleys, BUT they do not increase chain wrap/total capacity. Only a greater pulley distance center to center (ie a longer cage) will increase chain wrap/total capacity. The additional chain needed for the larger pulleys is used up going around the larger pulleys, ie the chain is functionally the same length as the smaller pulley set up. In fact, a larger pulley may decrease total cog capacity because the larger top pulley will come in contact with the cogs sooner. I would think that a Road Link could mitigate that but it won't increase capacity either, it just places the top pulley further from the cogs for interference sake.

My guess is, the selling point is that the chain doesn't travel as torturous a route as it does with smaller pulleys, ie doesn't bend as much going around them so it provides less friction loss.