Aspect ratio is, for more complex shapes the wing span squared divided by the wing area. For delta shaped stunt kites you get a larger wing span by increasing the nose angle, this also has the effect of decreasing the wing area. Both contribute to a higher aspect ratio. On the other hand the higher aspect ratio will reduce tip vortex drag and make the wing more efficient when it is in the airfoil region of flight. Wing Loading .
Wing loading is the weight of the kite divided by the area.
The lower the wing loading the less energy it takes for the kite to launch and remain airborne. To get really low wing loading your kite must be constructed from the lightest materiels available. As an aside, the optimum size kite for minimum wing loading is somewhere around the standard eight foot stunters up to maybe ten feet wing span. The reasons for this are that as the scale of the kite goes up the area increases as the square of the scale, but the spar stiffness requirements increase as the fourth power of the scale. This limits the upper size as the spar weight increases rapidly.