The difference between Diego the runner and the Guard pursuer was Vertical speed. Where Diego could simply leap on to a higher roof or structure the guard would have to climb up slower.  This combined with the winding and complex lay out of the city let Diego lose the Falcon, but barely. Finally he joins Dominique and 'Uncle' on the roof top. "I assume this is 'uncle' then? Well Dom I admit he does look a little like you," Diego joked. He then turns serious and says,"We best head for the ship then. I am sick of these roof tops already to be honest."