Antalya is more beatiful than Istanbul in every respect. You can swim in the city center in Antalya eight months of a year but you can't do that in Istanbul. There is no Old Town in Istanbul. Holidays in Antalya are the best. Of course Istanbul also has beatiful sides such as Istiklal Street, Taksim Square, Galata Tower, Galata and Haliç bridges, and the big ones. And Boğaziçi University, which is a very prestigious university. But against all ods Antalya is better.