My idea: If you do not mind paying cash to almost everything that you can get free you buy an Iphone. Iphone has the advantage of graphic quality and better games becouse developers do not make andoid version. But do not buy 6+ it bends in your pocket.
If you are going to play games and you dont want to pay for music and stuff you simply buy android. If you can get cubot x6 just do it. Its processor is better then my computers... If not you can get sony xperia z2.
If you are not going to use your phone like a psp just buy windows phone. It still has nice games. Gets updated frequently. Battery can last about a week if you dont use it. My friend has a windows phone he uses really frequent, surfs in the internet plays games and thing like that, and he said that he charges his phone once every 3 day.
Its up to you to decide though