That's a really hard question.... Im a sales associate for T-Mobile, and use an M8 for Windows. Before the m8 was Lumia 925, and before that, Lumia 810. Customers often ask me if I prefer the galaxy over the iPhone, and I can't answer. I dislike both of them. Significantly. If I wasn't convinced Google was Skynet, I'd probably go Google, but avoid the Galaxys because Samsung's Touchwiz had gotten so bad, it's like using a phone powered by the rampant Cortana that you saw in halo 5. However Ios, is a much more stable operating system. Though, it's difficult to navigate, and offers limited customizability. I often tell people I hate my job because personally, I feel Google and Apple are the two worst companies on our planet, and I have to push their products all day long. But, if I had to chose the lesser od two evils, today, it would be the iPhone. Lately, Google has become a far worse entity than Apple.
However, I'd never willingly leave Windows Phone.