I like all of my watches. I wear my world time mostly if I need to travel, 5159 and 5960 on most days, and 5970 on week ends.
If I have choose my most favourite one, I will go with 5159. Probably because I like all of the features that 5159 has : perpetual, seconds hand, and retrograde date.
From the wide range of its products offering, I can tell PP is really a smart company. They are good.... I am happy with the quality of PP.