I have the same choices that you have. I simply choose to use iOS. The 6 Plus fits perfect for me, since I don't own a tablet.the irony is that at least you have a choice. apple's walled garden approach is far from offering as open of choices as Android. besides, no one here is telling you your choice is wrong. it's just pretty much the same as other iphone users because you all really have limited choices. but hey, that's not a problem if iphones users are good with it. Apple's twisted version of Stockholm syndrome ?
Sorry I don't subscribe to the Samsung method of "every screen size under the sun in .1 inch increments is a good choice" mentality.
I use my phone as I want, and don't really pay attention to the "walled garden" as you put it. The apps that I choose to put on it, would be the same exact apps that I would put on it if I had Android or Windows Phone, so there's no difference there.