My Prince "goes both ways" too. He will usually squat but once in awhile he will lift his leg - sometimes he lifts his leg too high and almost falls over.
Since I also use potty pads in the house I'm glad he squats.
Have you noticed any allergy-type changes in Prince when the pollen count is high? Does he sneeze more after coming from outdoors? Or bite at his legs? I noticed Prince doing this but since the pollen has dies down he has stopped.