I am playing a Qarthadast campaign for the first time, at year 207 BCE or so. I have conquered all of northwestern Africa, Messana, and just defeated the Areuakoi (the Lusitanians were defeated much earlier and were rather easy to defeat, while the Areuakoi were quite tough), and I just got the reform in which I can make cities either Punic districts or native administrations. However, it only appears to apply to cities I conquered fairly recently. The Iberian cities I conquered decades ago (that are by now rather Carthaginianized), they don't get these options. Is it supposed to be this way?
Apart from happiness bonus and trade penalty for native administrations, and vice versa for Punic districts, as well as the differences in troop selections available, does choosing either of these lead to different options further down the road?
When you play, what criteria do you use for picking either for your cities?