I've been a long time android user but next week I'm buying an iPhone, I will still have my nexus but I'm wondering is it better on iPhone with playing these games (I play others, not just dragon story) than on Android?

Also I've already transferred my accounts before, apart from DS as I didn't play it then. Is it possible to do it again if I decide to move them to my iPhone? As I've heard you can only transfer once?