I recommend Puerto Vallarta, as it is bigger than Ixtapa/Zihuatanejo and has more night life, as you stated. Also, plenty more hotels and you can also go to Nuevo Vallarta and Punta Mita, if you can find a good deal on hotels there. I actually enjoy flying to Puerto Vallarta, because the airport is inside the city and you can catch a bus to your hotel, instead of paying for an expensive Airport Taxi, like in ZIH.

Puerto Vallarta´s malecon y beautiful and has enough night life, contrary to Ixtapa, which is more quiet during the weekend. So my recomendation goes to Puerto Vallarta for a single guy looking for those 3 things. I am also single but at the moment, I am flying to CUN as much as possible (twice a month) thanks to ultra low fares and also, really good hotel prices during weekends (even during the summer).