When I first got my 6 plus I still remained devoted to my iPad mini 2. Now some things are a little different. The Mac Rumors forum was redesigned in such a way that the mobile site is a pleasure to use. And my mini hasn't yet been updated to iOS 9 and had ad blockers installed. And it has only 1GB RAM so it's showing is age a bit and the faster iPhone 6SPlus is more and more becoming my internet device of choice. It used to be that I also did my online shopping on the iPad mini 2 but the color gamut problems again make me lean more toward my iPhone 6S Plus.
I didn't favor my iPhone 6 Plus before because it was always a bit laggy and prone to get me with inconsistent odd behavior when I least wanted to deal with such things. The new 6 S Plus is a smoother ownership experience so far.
However, if I upgrade to iOS 9, or upgrade to the new iPad mini, I'll probably go back to favoring the iPad for Internet use.
I read equally ebooks comfortably on either device.