Very interesting. Well, that's my concern about abandoning my Mini in favor of a 6+. I'd love the ability to have one device instead of two, but I do like the real estate of the Mini in a lot of situations. In fact, I rarely use my 4S.
I think the 6+ will be too big for you.
I was like you when using a 4S I had (and still have) an iPad mini and an 11"MBA. I found I was lugging all three around for work / travel / leisure etc.
Once I bought the 6, I dumped the iPad mini, because you can actually read and reply to emails on a 6, much better than on a 4S. Productivity ramps up and frustration goes down. Also I never really consumed media like TV / videos / Youtube as much as I did on my 4S and used my iPad for that until I upgraded.
The size of the the 6 is a big jump from the 4S if you never used the 5 (slightly bigger than the 4S) as I never did, but you get used to it almost immediately and wonder why it was never always that size.
For what it is worth, I tried to upgrade to a 6S+ last year, but this did not work out for me, as I could not get comfortable with the bigger size (and that is after using the 6 for over a year), so it went back after a week.