I was fortunate to have 2 contracts due for upgrade and got a 6 plus and a 6 yesterday.
The plus is HUGE and impossible to use one handed. But in both hands it is pure bliss! Screen is superb and seems more vibrant than that of the 6. Whiter and brighter too and we already know about the superior pixel density on the plus.
The 6 is far more sensible and extremely comfortable and natural feeling compared to the plus. Reachability is a clever innovation, that once used to, should make one handed use absolute bliss. I find it worthless on the plus as holding the plus in one hand I battle to reach the home button. I have small hands and it is just that big!!
Where the plus has a physical presence that's quite difficult to come to grips with, the 6 feels less imposing in hand than even the 5c it's replacing. In fact if you had told me that the bendgate saga was actually a 6 I would have believed that more. The plus is heavier, thicker, bigger and feels bullet proof in hand while the 6 feels petite and a little fragile.
Either way forget using either of these phones naked!! You've been warned...