This is mostly a selection bias. Given the wide variety of choices on the Android side, and the very obvious effect screen size has on using the phone, you have to be reasonably sure you want a big screen phone to actually bite the bullet. (Other factors are less clear cut and can be harder to decide between.) Since there is a good selection of screen sizes to choose from, you can often find something you want.
Contrast that with the two iPhone 6 people already replying to your post saying they think it is too big. As an Apple user, if you want a current year phone, you may have to go bigger than you want.
Android choice, for the win!
(BTW, I want! I'm pretty sure I'm gonna love the Nexus 6.)